Perhaps not a good idea (a gamble at least!).  I own and like the legit version of the frame, but I wanted to try the same frame but with a better fitting bar/stem setup.  This copy definitely does not share the same headset as the legit frame, since Canyon uses a proprietary quill stem setup.

Finished build (parts bin / new mix): https://imgur.com/a/DBR12Pr

Size 52 frame matte black
Stock 120mm stem
Stock headset cover
The One handlebar 36cm
Ultegra 8020 shifters
Jagwire cables and housing
105 hydraulic calipers
Dura ace crankset
Ultegra left side crank pm
Look carbon pedals
Token threaded BB
Rotor 53/39 chainrings with Rotor bolt covers
Dura ace fd
Ultegra rd
Pro Stealth saddle
DT Swiss Arc 1100 62mm wheels
GP5000 S TR tires 25mm
MT800 / Ultegra rotors 160/140
Zipp CX bar tape
Generic stem bolt Garmin mount from Amazon

First impressions after 3 rides (155 miles)

It is strange to review a frame like this.  Its a you-get-what-you-get direct-from-an-unknown-manufacturer frameset that costs so little relative to even entry level name brand frames that intuition dictates it should be, in the best case scenario, "acceptable", more likely some degree of "sketchy, problematic and/or vaguely frightening to ride"; unlikely that it would be "good". On the other hand, this is an SL7 in its tube shapes and geometry - the benchmark for a great all-round race bike - with a better bottom bracket (imo), more flexible headset out of the box, and 100-200 grams of extra weight (vs. standard and S-Works, respectively).  How should we assess the things we generally assume occur with name brand frames (like QC and strict conformance to the claimed carbon fiber layup) that might (?) be commercially infeasible at this price point?

I have ridden thousands of miles on a Tarmac SL6 sport frame (which was cannibalized for this build) and a Canyon Aeroad CFR.  Building up and riding this frame leads me to consider what the frame itself really contributes to the entire bicycle.  Geometry and the resulting fit is the most important contribution.  Second is aerodynamics of the frame and tube shapes.  Third is frame material / layup (i.e., desired level of stiffness or compliance in the right areas for the intended uses of the bicycle).  Last is weight. Ride feel, feedback, and comfort are dictated mostly by the contact points, with only a marginal contribution from the frame.  Tire width, pressure, and casing suppleness alone dwarf any differences in "compliance" between any reasonably stiff frames.

In the most important characteristics - geometry and aerodynamics - this bike effectively is an SL7. All the superlatives about handling and speed apply. If you are looking for an all-around race bike, this will fill that need.  The weight difference is quantifiable - materially heavier, though within the margin of difference made by a lighter seatpost, saddle and other finishing kit.  Frame layup and construction is harder to assess without cutting open the frame.  From a visual inspection, it looks clean.  From my initial ride impressions, the bottom bracket is stiffer than my SL6 - power transfer feels immediate, comparable to the Aeroad.  The fork does not flex when climbing or sprinting.  The stock stem combined with The One handlebar feels extremely stiff, but still has the vibration damping I would expect from a carbon bar and stem.  Against my expectations, the bike feels exceptionally good.  Whether that means that my specific frame has a good layup, or the carbon layup for this copy is comparable to the SL7, or it means that the layup, so long as its solidly made and not defective, doesn't have much noticeable impact, I don't know.   Maybe there is some hidden defect that will emerge in the form of a crack or failure after a few thousand miles, but I'm not sure what that would be. And I'm skeptical there is necessarily a higher chance of happening with this frame versus a name brand.  My Aeroad spent three months at a Canyon service center to fix two separate design flaws, one of which (the seatpost) wasn't really corrected.

I love this bike. This experience leaves me conflicted.  Does this mean that an S-Works Tarmac frame would be that much better? What this does leave me wanting is a Velobuild Premier version of this frame: pay double for an 800g version of the frame with an extra QC cert for peace of mind. I would feel better throwing DA di2 on that and doing a sub 7kg build. The benefits of the S-Works without the dentist meme branding or the anxiety of laying down a $5.5k frame in an office park crit.  Maybe I'm just describing winspace, yoeleo, et al.

I will reiterate - maybe I got lucky, and the median frame is missing parts, has holes drilled off center and is full of voids in the carbon.  Maybe carbon frame manufacturing has so matured that the default level of quality is high enough that the differences between frames are almost entirely geometry and branding, with the result that the carbon frame is the new carbon wheel. YMMV.

Build experience

Internal routing: more work with mechanical shifting but doable without any special tools. Just takes time and patience. Routing through The One handlebar was painless, I highly recommend it from that standpoint. I was concerned with the cable angles through the stem, but the shifting is smooth.  The clean look is satisfying and worth the extra effort. It seems popular around here to do mechanical disc brakes, but I wouldn't put brake cables through this stem.

Headset: it works. I read some reviews on this forum that suggested problems with headset play, but I have none at all. Maybe this has since been fixed. I purchased an FSA ACR headset assuming I would use that instead, but it left a large gap with the top of the headtube, and I ended up liking the look of the stock stem and the lower stack of the stock headset cover more anyway. 

Bottom bracket shell: nicely finished, no problems fitting the thread together bb. Stiff and smooth spinning, but will need a few thousand miles to assess for creaking, etc.

Disc brake mounts: did not appear to need facing, no more annoying to align rotors than any other frame (i.e., very annoying but works with some fiddling).

Just received a size 52 frame in matte black with the separate bar and stem.  https://imgur.com/a/F90D6Bd

Shipped 8 days after the order was placed and shipping took 7 days to Pennsylvania.  Overall, I'm impressed for the price.  Frame with derailleur hanger is 1020 grams - about 100g more than what I would expect a genuine Tarmac frame and 200g more than the S-Works.  Not bad.  The rest of the components come in at very respectable weights.  The bar and stem are quite a bit lighter than the Tarmac system and I could save 100g with a lightweight seatpost from Aliexpress. 

The frame and fork are clean from what I can see other than some imperfections in the paint work that I wouldn't expect to get through QC for a name brand frame. BB looks good and it remains to be seen whether the brake mounts will need faced.

I plan to build up with Ultegra hydro mechanical disc and HED 60/90 wheels from another bike.  I was planning on using an FSA ACR headset and stem, but the ACR headset leaves a noticeable gap with the top of the headtube and adds more stack than I would like, so I may modify the included headset cap to fit flush with the ACR stem, which should accommodate full internal routing and look clean. The included stem is actually a bit lighter, but I prefer the look of the FSA.  TBD.

Instead of the included 40cm bars, which look OK but are too wide for my fit, I will be using "The One" handlebar in 36cm.  Its pretty shamelessly "inspired" by the Enve SES handlebars, which I have on hand for another planned build.  Without having ridden either one yet, the build quality and finish looks comparable to the Enve and is a bit lighter.  Neither feel like they will noticeably flex under load.