I haven't had a chassis certed, but it's my understanding the inspection will be pretty thorough .(And pretty expensive. $400.00 I think?) At the very least, if you find sub-wall thicknesses, your car doesn't look like it would be that hard to back-half partially or entirely. It's not a good feeling to realize you bought a car that won't pass, and there are umpteen flippin' uprights that would have to be cut loose from a shoulder hoop that checks .002 too thin, EVERY other piece of tubing checking to spec. Ask me how I know...
Said shoulder hoop has a couple of grinding nicks from when I cut off the old cage, and has some small holes I suspect are snap-attachment upholstery way back when; I also suspect the existence of those holes permitted some (slight?) corrosion from the inside. My intent is tig them up and smooth them off for appearance. I forget where it prohibits grinding of structural welds, whether it's SFI or NHRA, but I don't see filling and filing a nick otherwise as a no-no.
One thing's for sure, there are a good several knowledgeable and experienced chassis building pros and others on this site who will give guidance, tips and tricks of their trade to us folks who want to do this ourselves. Ask me how I know...
Anyway, Welcome, Andrew. You'll find this site to be a gold mine.
John Williams