hahah I agree 306's get rotten up in there. Sometimes go unnoticed until the rear seats end up damp.
Yes they all get holes in there at the front wheel arch!
My diesel when I got it on 68k had a small hole there. easy enough to weld up though.
Honestly man, I wouldn't even wax up in there. just a fresh blast with clean water every time you wash it.
Abused 106/saxo I've seen rust up in there, it goes for the upper seatbelt mount - but only ever on lowered/slammed cars. The worst cars for rust are Silver and Diablo/wicked Red. No idea why, it just seems to be a thing!