Agree with all. Best tank straps out there. Never lost a tank.
Scubapro redesigned the strap a few years back. On the old ones, the open end folded inside, so you had to completely open the strap to make an adjustment. But this strap was maximally secure. On the new straps, the open end folds on the outside, so adjustments are a little bit quicker and easier. However, make sure to use that lock down slide (unique to the new model), which ensures that the velcro contact remains secure. (The webbing on the new straps is also thinner and more pliable. Overall, and esp because I use tank trim pockets, I prefer the old design. If anyone has a new set of the old model Supercinch bands to sell, PM me.)
On most Scubapro BCDs (Knighthawk, Glide, Classic, etc.), only one tank strap is used. This works not only because the Supercinch strap buckles down so tightly and securely. But also because of the way that the tank mounting plate nicely cradles the tank. Yes, the top of the tank mounting plate is rounded to align with the top curve of the tank. You can't really mount the BCD lower than this will allow without compromising the security afforded by the tank mounting plate--so, yes, you have identified a certain limitation with the system.
That said, when you mount your BCD as low as you can given the limit allowed by the top of the tank mounting plate, are you finding that you cannot reach the tank valve when in a horizontal position underwater? Or when standing on land and your rig is sagging in the back? When I used to dive a Classic, and even now diving a BP/wing, I only loosely buckle my waist belt on land and simply allow my rig to sag until I get into the water. My very first order of business once I reach depth and stabilize horizontally is to adjust my waist belt to secure my rig so that the tank is where it should be on my back.
