If they are like polaris's self peircing rivits(I am sure they are), then they weld the aluminum togeather with the rivit as they peirce thru..that said..they are a bear to get out, what I have found to work decently is to grind the head off flat, then use a air hammer with a flat ground point that matches the rivit diameter with a 2"x6"x1/2" flat plate to use as a backer(drill a hole slightly bigger then the rivit body so it can be driven right thru the plate), the plate acts as a backer to keep the air hammer from bending the sheetmetal up..it takes 2 guys and alot of patience..but it works pretty good..to reassemble I would use solid aircraft rivits(they use a airhammer with a special mandrel to drive the rivit, and a steel backer for the rivit to swedge against), again, a 2 person job to do right..but stronger then any pop rivit...