eeek, that would just make me itchy...
buddy of mine had his entire rack with two bikes included take flight doing about 100mph while driving through CO..
the INSANE part, it landed on all fours... slid on the pavement for 100 yards or so, towers were a total loss and there were some bent parts, drop-out on one of the forks was a little jack'd up but, somehow, the rack didn't tumble and explode like you'd think it would hitting pavement at that speed.
Yeah, it was a one time thing, definitely not something I do on the regular. That horror story is definitely enough to keep me below the century mark with bikes on top haha