Hitch rack + adapter = stable?

I have a Thule 2-bikes hitch rack on my Acura RSX (hatch back, rear windshield has no rim.  You don't want to mount anything on glass).  THis is the only way I can put a rack on my car. 

Have had it for over a year and works well. 

Do you reduce the rack down from 2" to 1.5" or is the rack a 1.5" tube?

I'm really worried about the reducing couple adding a lot of slop to the mount.

I thought about welding - but that leaves a 6 inch tube sticking out the back of the car.  Not the best or safest option - and I know I'd be the one busting my shins on it all the time. 

First thing I checked . . . .

A little more surfing, and I found this:  http://www.autoaccessconnect.com/anradeforhim.html which I think might do the trick.

I'll let everyone know next spring.

I have a 1.5"

My car doesn't even have a hitch to mount anything on.  My mechanic installed the bracket at the bottom of my car and the only a bracket that comes with a 1.5" hitch fits my car. 

Your bike isn't that heavy.  Shouldn't be a problem.  Just make sure you don't back into a wall.