The 3/8" bolt is more likely to elongate the hole in the top of the frame rail than the 9/16" tube... I think you're worrying too much about nothing. This isn't a 2000 hp Pro Mod.
I got the idea from the BBD pages on "Make your own elephant ears".
i agree it won't be a problem for you, i just wanted to point it out for anyone reading your post. wasn't trying to diss your car at all, it looks great and no offence intended :thumbsup:
neil.