I am currently fixing press studs for my tonneau cover using rivets for the male piece. In two locations I cannot get a washer on the back of the rivet ( fixing into fibre glass ). I am concerned that repeated pulling on the press stud to remove the tonneau will eventually result in the rivet pulling out. What are my options? I had thought of using M4 rivnuts but I have never managed to set one of these without stripping the thread - may be better in steel? Are there any other clever fixings that might do the job? I am restricted to head diameter of 7 mm to fit inside the male press stud. Any ideas appreciated.

I used a drop of SuperGlue on the threads of a small c/sk stainless self tapper. Hope I don't need to take them off

Try load spreading rivets.
Load Spreading Aluminium Pop Blind Rivets. LSR 4.8 Diameter. Choice of lengths

Thanks loggyboy, top tip. Never heard of these before.