I tried out the SeaSucker suction cup roof rack for my bike on my G37 Sedan and took some pics. I drove about 12 miles, some road, mostly highway, 65-75 mph, no issues at all.

I bought the SeaSucker mainly for my other car, but it seems to work well on my G37 also.

 

That's interesting. When I used to put a bike atop of my car, I'd always put my garage remote somewhere other that the usual clipped to the visor location. I was worried that I'd forget the bike was there when coming home and entering my garage. With a vehicle that has built in home link buttons, I'd put a piece of blue tape over the garage door button to remind me...
Nice bike.

 

That's pretty cool indeed...where did you get it?

I have to be honest though, I'd be scared to death to put any of my bikes on my roof attached by suction cups???

 

SeaSucker Vacuum-Mount Bike Racks

 

Looks very cool. I agree with TheIvoryG, I might be a bit chicken to put my bike on the car with that - afraid it might come loose.

 

Putting my $5k bike on top of my car via suction cups would not sit well in my stomach lol