Arnie,
Was thinking about this, and although I initally thought solid rivets would be the ideal job, if its GRP and ali, its likely going to be out in the middle of a panel some place that is awkward to get at both sides to thump the rivet over, and it could be tricky to do without damaging the GRP. Definitely worth looking into, in my opinion.
Bearing in mind you have 4000 to do, I'm guessing cost is going to be a bit of a factor...aswell as speed. An alternative might be to use something to give the dome on the outside (Maybe a hollow "solid" rivet, like this here) and then pop rivet into it from the inside. If you could get something like a domed nut, without the nut bit, it would be ideal.
I've never used the hollow rivets, so not sure how they look or rivet up when used as a normal solid rivet (i.e. thump the end with a hammer).
The other thing you should consider, but again I've never used them, is a kind of screw/nut arrangement which some rivet manufacturers do, see here for example. The difficulty you're going to have is depth, as unless your GRP is very thick, I doubt you could get any more than a few threads width within the thickness of your two panels.
If you could do something like run a 1/4" thick bit of flat aluminium bar, say 1/2" wide, along the line of the "rivets", you could stagger them and actually tap the bar and screw in from either side. Major work, but an option if you're stuck.
If you have a local model engineers soceity or anything, speak to them about solid rivetting. They'd be able to show you all the options and maybe even lend you what you need.
All the best,
Willie