Blind rivets are used in aircraft all the time. This includes areas of the outer skin that is susceptable to high pressure at 35k feet. A good sealer between the two pieces of Aluminum, some blind rivets and you're set. BTW, What's a well nut?
http://www.zenithair.com/kit-data/ht-86-12.html
http://www.zenithair.com/kit-data/ht-87-1.html
If you do, use a quality rivet. Some are very tough, some are cheap.