(ET) Pop-rivets, body rot

[Allan <allanhv worldnet att net>]

I was also looking at replacing the pop rivets and repairing some of the
rust at the lower rear battery compartment.  The lower part of the
battery compartment is rusted right through, to the point that I'm
afraid if I bounce on the seat the box will collapse!  The frame looks
fine, but the battery box is in trouble.

Any advice / comments on how to repair this?  Also, it looks like the
box is rusting out from the inside, probably due to battery acid,
despite the plastic tray.  Any suggestions on how to prevent this
problem in the first place?  I'm considering lining the box on the
inside with fiberglass.

Thanks,
Allan