I have the T2 with the extension for the additional 2 bikes. I chose it because I needed to travel with two road bikes and my wife's and daughter's Electra Townies. No issues with different sized bikes, including the mis-matched wheelbase lengths. Not sure of the issue with using the rack on carbon bikes, since you retain the wheel, not the frame with the T2. I'm just careful to engage the clamp on the tire, not the brake caliper and it seems to be fine.

Main problem with the rack is that it is HEAVY--my wife can't put it on and off. Also, on our RAV4, the clearance is a bit too low when the rack is on, we usually bottom out, even when it's folded up. On the RAV4, we also can't open the rear hatch unless we swing the clamp arms outward and down (rather than just folding them down onto the rack itself, if this makes sense).