Placed my order for a VB-R-168 on Friday last week. I ordered the 52cm Frame with a 400/90mm bar stem combo and had confirmation from Chris before ordering that both the frame and bar was in stock.
I'm 170cm tall and according to the Specialized SL7 size chart I'm right in the middle of the 52cm and 54cm frame sizes so decided to go for the smaller option.
I am a cm shorter than you, with 77cm inseam. The Specialized sizing tool and chart suggested to go for size 52, and instead, I've ordered the size 49 with a 400/90 bar.
I used my current bike as my sizing reference. It's a 20er folding bike, but I've installed a drop bar on it. I've played around with the stem lengths, handlebar heights, and brifter angles, to find the right geometry for me. From those experiments, I've concluded that the horizontal distance between the seatpost and the horizontal part of the handlebar, center-to-center, is around 60cm. Now, the shortest stem they have for the integrated bars is 90cm. 600 - 90 = 510. That's the size 49's effective top-tube dimension, give or take.
There's also a note in this thread that their integrated bar is curved forward. I assume that the curvature is already factored in the 80mm reach of the handlebar, but if it's not, then I'd have a minimum additional stretch. Other than that, the seatpost has a setback (2cm?). If the frame is indeed too small, I can move the saddle back and it will then have the ideal effective seat tube angle.
Also, I'd probably get an option to slam it, if my back allows.
Let's see if indeed I've ordered the right size when I finished the build.
The problem is, although I ordered it as a plain frameset, it's still waiting for the 400/90. In the last contact with them, they said that they will send it out at the beginning of this week.