When you rivet the band back on as you know the rivets generally penetrate the top of the lip. This opens up the possibility of leaks
from water collecting on the top of the band and lip leaking into the cavity formed by the junction of the two parts and the fiberglass mat joining them on the inside.
This cavity can be formed and carry water that leaks
in quite a distance from the leak.
Be careful to caulk the top side of the band only so that any water that gets in behind the band can leak outside and also take care to seal the joining area as carefully as you can.
I would not worry about installing a large number of rivets as the band, once riveted on the ends and a few spots around the trailer will not come off, but each river offers a place to leak and any hole that allows water ingress is a problem.
Use a good quality sealant to caulk the top of the band to the trailer side and no sealant on the bottom.
Been there and done that!
In my case I had a leak that showed up as a leak at the junction oc the belly band backing and the front of the door jamb. The actual point of water ingress was in the front of the trailer, probably 4 - 6 feet away.