I completed my build approximately one month and 1,000 km ago, and I thought I would share some impressions and experiences. Communication with Velobuild went well, as did the tax-included shipping to Europe, which took just under three weeks. The frame size is 49 cm, and I chose the color "glossy pearl white" after seeing some great pictures earlier in the thread. The color looks just as impressive in person, although there are some minor imperfections in the paint (a couple of matte spots and some "orange peel"). Nothing I can't live with for the price.

I ordered the frame without the handlebar but with the stem. I wouldn’t feel comfortable using the stem (nor did I really intend to) based on the quality of workmanship it exhibited. I tossed it in the bin. Instead, I modeled and 3D-printed a custom transition piece in CF-reinforced nylon, between the stock headset dust cap and a genuine SL7 stem with corresponding spacers. It turned out quite well.

I opted to use a DEDA 70 mm expander plug, and the installation almost ended in disaster. It was oversized for the fork steerer’s internal diameter, so I had to turn/sand down the diameter of the end pieces. However, I misjudged the flexibility of the middle piece, and it began to get stuck about three-quarters of the way down during installation. I had to resort to an almost uncomfortable level of force, hammering it down with a rubber mallet, but it got there in the end. On the plus side, I’m sure it will never slip. Be careful if you plan to use this expander—don't repeat my mistake!

While the included headset bearings seemed fine, I installed stainless bearings from the start, hoping they’ll be "set and forget." The brake caliper mount faces were not properly masked during painting, so I had to carefully file/sand them down. To my relief, I haven’t encountered any alignment or rubbing issues so far.

Apart from the issues mentioned above, the build went smoothly without any major concerns. I used 105 Di2 except for the front derailleur and cassette (Ultegra), and rotors and chain (Dura-Ace). Routing the Di2 cables and brake hoses went smoothly after drilling/Dremeling out the hole in the front derailleur port. I bought the 3D-printed battery seatpost wedge that was linked earlier in the thread. The wheels are AR56 from LB, and the handlebar is PRO Vibe aero carbon. The included mounting hardware has worked fine with the PRO Turnix carbon rail saddle.

I had concerns about the speed-release axles, but they’ve worked flawlessly so far, and I would even say they're convenient. The small hex screw holding the derailleur hanger in place needs to be quite loose, though—otherwise, the thru-axle binds in the threads as it misaligns the hanger. I secured it with Loctite, and it hasn’t caused any issues since.

Would I buy again? Yes!

I'm in the process of ordering a 268 frame but would appreciate some advice on the headset & stem. At risk of repeating an old question - has anyone successfully used a SL7 stem/spacers/transition kit on this frame? I understand it's possible to use a FSA no.69 headset with any stem of choice, but would prefer an integrated look with the SL7 stem.
   
In the 168-frame thread there's been some discussion about 3D-printed transition pieces for the Allez Sprint. Unless I misunderstand, this round design will not match the 268 frame, and will leave a gap where the original transition piece is? Has anyone gone down this road?

https://www.printables.com/de/model/171982-specialized-headset-cover-round-to-sl7-spacersstem/remixes
https://www.printables.com/de/model/555935-velobuild-vb-r-168-specialized-tarmac-sl7-headset-
   
On a similar note, is there a consensus on the quality and durability of the included headset bearings? Would it be advisable to replace them with FSA bearings for peace of mind, regardless of the stem question above?

Thanks!