At first until I moved the cam strap way down, it was riding behind my shoulder. I might try a slightly longer bungee. I just got a side mount butt plate. have not had it in the water yet. May make the difference, since I now have a rail, instead of a side d-ring.
This doesn't make sense. The cam strap on the tank should be positioned so it is in line with where you clip it. If on a waist d-ring then in line with the waist strap. If on a butt plate, then in line with the rail. With AL80s you shouldn't need a butt plate. They are light enough to not require that. You want the valve and 1st stage snugged in your armpit.
Take a look at the photos on this page for proper positioning of cylinders. Scroll down for the AL80 photos but even the steel photos show you proper positioning.
Sidemount Photos « Rob Neto