So you want to get in a position where you're not relying on anything for a buoyancy bailout. On the other hand you, don't want a whole bunch of gas in the wings so they're jacked up which is going to slow you down, cause more drag and be more unstable in order to stay up. You just want to be fine-tuning your trim. You want to be able to put enough gas in your drysuit to stay warm but you don't want to have to jack it up and jack wings up because you're too heavy. Conversely, when you're up low on gas or whatever and you've got maybe some stage bottles on you don't want to be having trouble staying down and not being able to put enough gas in your drysuit at the end of the dive when you need the warmth the most. That's a big part of this whole system. That's why we don't dive steel tanks with a wetsuit. Body cavities compress, all the materials compress, everything compresses, you get down and you can't get up. I bought a set of Genesis 102s 12 years ago when they first came out. Jumped in with my wings, harness, got to 250ft and completely lost all my buoyancy. Dropped to the sand at 300, luckily there was a floor, and I crawled up this wreck, all the way up the wreck, up the tower of the wreck, until I got back to 260 or 250 and then I could gain equilibrium. Burned off a little gas. It's ridiculous, you don't think it's possible. It's amazing how negative your body and everything gets when you compress. That was a real shocker. So it's generally better to have aluminum tanks with a thin wetsuit and a weight belt so you have droppable weight of some kind. And with salt water and a drysuit and 104s, you don't have the same issue. But anyway, these things have to be thought through for every type of diving. That's a big part of the system. It's also a big part of being slick and being quick and not being over or under weighted. With stage diving using aluminum bottles you can float the bottles up on your lift bag, your deco line, your up-line, whatever you're using. You can fire the bottles up if they become too buoyant at deco. That's what we do. We just let them go, stage bottles or deco bottles, let them ride up the line.
