just managed to sort how to make a topic and message.
I am near to fitting the aluminium side panels but need
to be within the IVA regs on pop rivet sizes and spacing. Can anybody help.

there are no rules about spacing for body panels - it just needs to be secure and not fail any of the general radius tests from my memory.

May be an idea to download the IVA manual and double check i'm correct. Good luck

Thanks for your quick report.
What you say makes a lot of sense, ie good sound engineering practice.
I looked in the original Ron Chapman manual (came with car) and said
to use 3mm pop rivets every 50mm. Did seem an over kill, I would be forever
drilling.

a lot of people use a sealant a well as the rivet's. effectively gluing them as well as riveting.

The side panels on mine are bonded with Sikaflex, no rivets. On the road 9 years, not fallen of yet

I also used a bond type silicon, although the car has only been on the road a year now, but the panels have been stuck on the chassis for over 22 years now from when they were first put on !

Jason