I guess is it's probably tricky to maintain rivet temperature - as soon as it contacts the hull, all the heat is going to flow out and the rivet is going to coo

I guess is it's probably tricky to maintain rivet temperature - as soon as it contacts the hull, all the heat is going to flow out and the rivet is going to cool very rapidly. That would presumably have a negative effect on clamping pressure, because the rivet wouldn't shrink so much after it's been hammered in place. I think the guy upthread had it right, however: probably the main difference was the manhours involved per rivet, just because you seem to need like four people working on each rivet at once. And, honestly, if a task is just horrible to do, that's got to have an effect on productivity.