I just started diving a low pressure 108 and removed 9 lbs between changing to my aluminum backplate and reduce my belt to just 2 lbs. I was wearing a 3mm full wetsuit and probably could have gone without the belt completely. I did feel the buoyancy swing as I used the air supply but was able to stay submerged for a 3 minute safety stop at 15’. The best time to do a buoyancy check would be at 500 psi regardless of the tank size and pressure rating.