My polaris has the tubes attached with a screwed-on flange at the point where the floor hits the tube. I have no idea what else goes on between that flange and outer hull to tube joint, but that outer joint has a glued-on strip of hypalon that goes from the tube, across the joint, and onto the aluminum.
As far as I know, the aluminum is etched using an acid primer, then glued using the manufacturers standard hypalon glue, Bostik 2402.
If you want to make sure, you can e-mail him at firstname.lastname@example.org
; his name is Guy.