The base plate has worked wonderfully. It has allowed me to get in a more agresivo position since the amount of holes allow for much better adjustment of the bars. Also, being able to move forwards and backwards the BTA system helped me figure out the best setup for me.

As for the rails, yes, I’ve heard theses thin rails for moving ups and down bottles are not sturdy enough for holding a bottle as the amount of force can break them. I had seen the rail from Tririg but getting it to my country makes it almost double its original price.

Your rail looks amazing, and I think I could get it machined at the same place I got the baseplate made.

Here are the files for the rail.

And here are some files. I got the bridge and the angle piece made from 6061-T6 aluminum with a black hard-anodized finish.

The bridge has a variety of mounting holes, on a slightly different pattern than the original bridge. I also pre-angled the mounting pattern inwards by 1 degree to get my hands a little closer together.
The angle piece requires flat-head M5 bolts which attach the angle piece to the bridge before being attached to the base bars.

Flat 90 degree SRAM wireless blip mounts: https://www.printables.com/model/1475910-wireless-blip-holder-for-time-trial-and-triathlon
Tool box for Large frame: https://www.printables.com/model/1475920-frame-tool-box-for-velobuild-tt-023-triathlon-bike
Closed back elbow pad extensions: https://www.printables.com/model/1475931-closed-back-elbow-pad-extensions-for-velobuild-tt

I read this whole thread as I was deciding on my new TT bike last winter, and it convinced me to order. My previous TT bike was a used 2011 Garneau Gennix T1 Large, and I was looking to be more comfortable for my first full Ironman in Ottawa this past summer - more adjustability in the front end and bigger tire clearance. I am 5’8” (173cm), 155-160lb (70-72kg), and went with a large frame for more reach/stack since that fits me best. I did get a bike fit on the Garneau, (and the Velobuild once it arrived), and the fitter agreed that a large frame is right for me.
The order process was great, got them to add the 2 bolt holes on the top tube for a bento box (though I have not used them yet). Went for a black/white paint scheme and added my name in the paint at the seatpost. This was the 2nd frame I’d built from scratch (first one was a custom drop bar titanium mountain bike from Waltly Ti), but I’ve been doing my own maintenance on my bikes for a while. The build was very straightforward, with the usual difficulties of fully internal cable routing. I did crack the stem as I was tightening to the recommended torque (5Nm), and Chris from Velobuild sent out a new one – though I don’t trust it anymore, so I’m looking for other options now that I’m done racing for the year.

Parts List:
Frame: Velobuild TT-023 Large
TT Bars: Included with frame, but I added a custom 3D printed extension off the back that replaces the (too) soft yellow foam over the screws and makes a closed back for the elbow. Also adds a bit more length to the extensions which I found I needed. Custom 3D printed SRAM wireless blip holders. Textured heat-shrink for the grips, as I’ve seen in a few posts in this thread
Stack Angle: Custom machined aluminum block for additional 9 degree angle
Base Plate/Bridge: Custom machined aluminum bridge for a bit more reach and a BTA bottle mount
Arm pads: CeeGees 10mm TriRig Scoops Ultimate SL for full padding along the forearms
Garmin Mount: Custom 3D Printed mount that fits just between the bars at the front. Very large platform zip-tied to the bars, covering most of the area between them.
Brakes: RideRever Triva
Rotors: Shimano Ultegra
Shifters: SRAM Wireless Blips
Bottom Bracket: Token Steel Bearing T47 Threaded BB 47mm for 24mm cranks
Crankset: 160mm XCadey 24mm spindle
Power Meter Spider: XCadey XPower-S Gen 2 110BCD-4S
Pedals: Shimano 105
Chainring: 1x 54T Pass Quest
Chain: SRAM Force with Silca wax
Cassette: SRAM Apex XPLR 12 speed 11-44T
Derailleur: SRAM Force D2 12 speed XPLR
Wheelset: Yoeleo SAT C88 DB PRO NxT SL2
Tires: Continental Aero 111 29mm on front, and GP5000 30mm on rear
Disc Cover: ABS Sheet with electrical tape and zip ties
Aero Bottle: Canyon 650mL Fuel bottle, Fidlock magnetic mount
Toolbox: Custom 3D Printed box fitting the aero bottle and the frame. Inside I fit my pump, tupe, plugs, extra tubeless valve parts, multi-tool, hex keys, tire levers. Take the top cover off, and pull out an insert with slots for all the individual tools.
Saddle: Ergon SR Tri Front (not settled on this yet, might tri that ONIRII 3D printed TT saddle)
BTS Bottle Holder: For me, the 2nd seatpost bottle mount hole is hidden inside the frame, so I spent some time to come up with a much better solution. Custom design – yes, it fits within the 30x30cm box rule, but it is a little heavy (~700g, but I’m working on improving that). 2x1L Bottles face forwards so there is much less risk of ejecting. They are also quicker to remove since you don’t need elastics on them to keep them in, and they are much easier to reach. I haven’t done aero testing, but it definitely looks fast – the goal was to have then follow the curve of my back. The pictures don’t show it, but the bottle also angle outwards for easier access since you reach around the side of your body, not directly over your back (and maybe helps with aero as well)

Ride Review:
I haven’t seen anyone else put an XLPR groupset on a 1x TT bike – this forum seems to be the place for unconventional builds though - I think it works great! I am not too picky about cadence, generally average about 95rpm in races. This bike is quick, it just wants to go fast (2nd fastest bike split at IM Ottawa this year). Liquid nutrition for my races, carrying up to 3.65L on the bike and grabbing water from aid stations (possibly more with a different front hydration setup). Much more comfortable than my previous TT bike as well, but there are many factors that go into that (tires, fit, saddle, etc.). On windy days, the deep front wheel gets blown around a bit, but that’s entirely expected.
The headset bearings seem to have rusted after my IM – sitting in T2 all day with sticky carb drink maybe did it. I’ll be replacing with higher quality stainless steel bearings when I replace the stem.

If anyone is interested in the custom parts I’ve made, let me know – I’ve seen a few people in other posts asking about angled spacers (I have been considering starting an online store)! I’m happy to share the files for the 3D printed parts, but they are in constant revision, so I’d have to lock down a design.