Mine was made for the AL80s. It should work for anything 7.25" in diameter. As you said, it should work for anything similar and shorter.
Yours looks nice! I was happy that the necks were avoided because I didn't know if that was a faux pas. That is why I also left the gap. During travel the straps would hold the tanks unless I get rear-ended, where the 1x8 would kick in hopefully. I like your design. I would prefer no play. It may nag on me enough to take a quarter inch off the runners on the "bottom" end.