i dont think you have anything to worry about. i know a guy runing mid 8's w/ T tops on his GN wink
you may recall that vidio of the GN with twin turbo's coming out of the hood on the dyno smokin the tires? thats him.
of course, his car is braced properly. just do the GNX back seat mods and a few other things and it should be fine.
Another Guy I know of has been in the 10's with his.I have the braces, and drove mine all summer with so far with no less than 20+psi and drag radials and there are still no pillar cracks or any other problems to be seen.T-top cars get ALOT of bad press,both version hardtop and t-top have their drawbacks, but nobody can say for sure that one is better than the other.It's all in your personal preference,I have had both and will take either and love them the same.