Mounting bolts for cabrack

Has anyone had issues with the bolts that go into the roof not fitting? I bought my buddies prinsu and it came with all the mounting hardware from Prinsu. The ones that he recieved were standard, and he used an impact to get them into the thread. After taking it off his, we looked at the thread on his roof and it is completely useless now. We went to the hardware store and found the proper bolts (metric), but they only had steel (not stainless), so it is a VERY temporary fix. Has anyone else had this problem? I cant find the right sized bolts that are stainless steel anywhere, does anyone know where I could get them?

 

Probably 6mm x 1.0 SS button head cap screw, black oxide is what's included with Thule racks and that seems pretty rust resistant as well.

$13 M6-1.00 x 30MM Button Head Socket Cap Screws, Allen Socket Drive, ISO 7380, Stainless Steel 18-8, Full Thread, Plain Finish, Flat Point, Quantity 25 by Fastenere

https://www.amazon.com/M6-1-00-Butt...5047874&s=gateway&sr=8-1-fkmrnull-spons&psc=1
Mine's an AC so I don't have the welded in nuts but you already know the size, just search that size in SS button head cap screw.

Pick up a 1/4" hex driver that fits the cap screw and start each screw by hand and make sure it threads easily before tightening with any leverage tool(ratchet, screw gun, impact driver) an impact driver can easily cross thread but still fully drive the screw and fuck the threads.