The semi hollow rivets turned up today, so with a glint in my eye and a handful of rivets I disappeared down the shed for the evening.
Using guesswork and black magic, I made up a former to hold and roll the rivet end and welded these to a sturdy g-clamp. Results are 50/50, the tool works okay but I now have to find some 3/4” rivets and modify the tool to get the right angle on some of the rivets.
