AH! Finally a question I know a good deal about!
I put in a bazillion or two rivets in military aircraft.
If you're talking solid rivs, I don't like the idea of using a chisel to "behead" them. Might stretch the hole. Drill them out. Usually, the rivit is going to be a nominal size (3/32, 1/8, 3/16, 1/4) and the hole is drilled slightly over with a number drill (#40, #30, #20, #10 respectivly). Get a nominal size drill, center up good, DON'T wobble. Drill in about the depth of the factory head, no more. If you did good, tilting your drill will pop the head off. You may need to use a punch, but that's OK, then use your punch to drive the shank&shop head out of the hole.
Now, you should prep the hole with some alodine - it'll slow corrosion. Turns the Al slightly brown. Clean the metal off real good with some scotchbrite, wipe with a solvent rag, apply alodine, wait a few minutes, wipe again.
Install your riv's - use wet paint or sealant. It'll seal better, and again, less corrosion. The shooting/bucking described by Geaorge Coates is on the mark. We had signals for the times we DID wear ear muffs, which wasn't often. ( I still hear pretty good)
Shooter pushes rivit in. Bucker presses it back at him to let shooter know he's on it. Shooter pushes it back in and shoots it.
Bucker signals -
One tap, smack it again.
Two taps, That'll do.
Three taps, mark it for removal.
I don't know what alum. riv's are avail. from Jay-cee
Fairly soft ones - MS20426B for brazier head, MS20470B for countersunk head.
If you want a little harder, replace the "B" with "AD".
C088/089 would prob. be overkill for your boat. All the above are supplied anodized.
And when your'e done, you can go to SWMBO, and sing a few verses of "Shake the rivits from my hair, shake em loose and let em fall.."
Rudd, ducking.