please excuse my first crude attempt to see if the theory would work.... the idea is i will weld up the inside of my armour where the plates meet...the sections hidden by the angle bar.... then for the frame rails i will drill and plug weld the plates to the frame rails....the fake rivets with some locktite added will be wound on and should give the correct appearence. but majority of strength taken up by the welds... i have done a crude load test with the rivet under tension and i could hang a road wheel from it without it pulling.
i took a rivet out of the original armour and the closest coach bolt (18mm head) was the standard M6 i had tried the M8's but the head was slightly too big and the shank size did not leave enough material on the rivet to thread.
some will probably say LOTS OF WORK THAT ! and they would be correct but... using a pillar drill i drilled and tapped 3 rivets in 15 mins. on a lathe with a jig i can center the rivet easier and will be able to produce them much quicker.
for those who may not brave hot rivetting.....i tried and failed.... this may be an option
sorry if i have hijacked the thread Shaun...i suppose its kinda relevant to where you are with your build.