I'm on a size Medium with aerobars fully extended (i.e., they are slightly recessed into the armpad clamps, actually). Some more details on my fit numbers are:
Saddle height: 767, setback -19mm
Arm pad stack: 639
Arm pad reach: 460
Crank length: 165 (I switch the crank to 165 from the stock 175)
I feel like I need to get longer, but at the same time, I feel like my weight is already WAY out over the front wheel, which has me wondering if I should have gone with a Larger, though standover height would be a concern (860 mm inseam). As you can see I am using the Canyon angle brackets, and I also have adapters to make the aerobars wider.
Please let me know if you need anything else.