Windshield frame

[NHGuy]

I have a walk through windshield. It's mainly flat and nearly flat glass sections in an aluminum frame. I have had it apart on 1 side when I replaced the front glass after an accident. The frame isn't very solid any more, but truthfully, it wasn't very good before the repair either. So how would you go about tightening it up?
I used aluminum rivets when I put it back together. Should I be trying to find stainless rivets? Should I drill to the next size, or try the same size 1st?