Hey, looks good! The photo is a bit small so I can't see as well as I would like to.
It looks like you might have overlapped some of the "hinge cuts". What I did was make a "V" cut at each hinge point so that there would be no overlap of the flaps and everything would stay flatter. The brand of rivets I used are Olympic and they are aluminum too. The shaver tool is the expensive piece of the equation, but I already had one since I work on my old Airstreams.
After explaining to you twice how I made mine, I knew you were going to make one of these tanks, just not in one afternoon!! Good job!