I bought 2 of the Cooper-T 90 deg adapters a few years ago to allow the tank to hang down. The 9 oz steel tanks work fine without an adapter, but they are too heavy on the front of the rifle. The problem with the Cooper-T adapter is that I had to try to shim the adapter to get it to point straight down, which took a lot of trial and error. The set screw solves that problem. In addition, a 9 oz tank hanging down is cumbersome. That's why I bought some 4 oz tanks recently. Although 4 oz vertical tanks work well, using this adapter would be an improvement. I like the lighter 4 oz tank better than the 9 oz tank. Now to decide if I want to spend another $30, or $60 for both QB79's. Maybe if I tell the wife real gently.
2 Mike Melick tuned up QB79
1 Mike Melick tuned down AR2078A (60 shots/CO2)
3 pistols (Daisy, Gamo and Beeman)
4 other rifles (3 old springers and Daisy target)
Crosman custom 2400KT - 18" .177