Each to there own. I have been using them for 25+ years with no mishaps. I trust them more than a tube of sikaflex.
https://blog.baysupply.com/5-tips-for-uses-and-installation-of-rivet-nuts
Can you not drill the roof from the outside, wth a depth stop on the drill bit and insert rivnuts and fix off of them. It's what i'd be looking at doing if i was in your position. Just a thought.