Lift was definitely a concern for the engineers at Front Runner for their full length rack.
Wasn't there a member a while back with a Gobi (memory fails me), that went through a car wash, and the rack folded up? Seem to recall they had to stop the car wash, then had to bend it back down enough for him to drive out.
Not sure I would trust the front end not being bolted down.
ETA : found it, Baja rack :
http://www.toyota-4runner.org/general-discussions/191337-$15-carwash-%3D-$4047-18-damages-repairs.html