Hp100s hang horribly (they are -9 lb full with nitrox) and there's no way to stop it unless I get a bigger butt. I've seen this in my own razor and with an xdeep with the rear clips moved all the way to the spine web. Even with a zero leash length on the rear clip, the clip itself is a good ~4" long. Combined with a 7.5" tank that is a total length of around over 11", plus the width of the Dring attachment on the butt (which varies but is at least 1" for a total of 12 or 13") the tank will end up hanging below the plane of your body unless your waist/butt is wide or your beer gut hangs lower. With a 31" waist I basically have 8" from the center of the spine in the back to the forward most part where the tank ends up being 'below' me. Hiking the necks up with an oldschool bungie helps but there's only so much rotational force the bungies can apply to "rotate" the tank up and get the lower edge above the plane of your belly.