that would be 1-2lbs positively buoyant...... can't have any lbs neutrally buoyant, 0 is 0.
Always amazes me how many people keep screwing around with trim weights when proper body positioning will fix the vast majority of issues. You don't see most technical divers using trim weights, the sidemount guys have some leeway with it, but even they usually only use a 1lb trim weight on each shoulder strap. Between properly balancing the rig as far as buoyancy, and positioning the tank properly, you can fix most seriously out of whack trim problems. The biggest problem with buoyant head is people don't dive in a proper body position so as soon as you allow your knees to start falling the rest of your body will follow. This is analogous to how you can float on your back as long as your chin is tilted up, but as soon as you bring your chin to your chest your whole body will follow it and you will go vertical. Diving is exactly the same way, if you don't have your torso and thighs in line, and your feet are sticking too far out, you will increase the moment around your CoG and you will go head up feet down. If you get in a proper diving position, you move the CoG close to your head and you will balance that way. You want the CoG to be variable so you can make these types of movements just by body positioning instead of finning.
I.e. Want to go head up, all you have to do is extend your feet a few inches while arching your back and you will go head up.
head down, tuck your chin forward and bring your feet a few inches close to your butt and voi la, you are now head down
roll to the side, extend the leg on the side you want to go down a few inches and chicken wing out one arm, and you will roll over on one side.
No hand motions, no fin motions, just slight adjustments to your body positioning and you will do all sorts of acrobatics. You can also compensate for slight variances in gear changes to the CoG. Good divers can dive in trim, with the tanks moved a few inches in either direction, you will learn to compensate subconsciously, same as you have to when the tanks get empty and there is a few inches of shift as the butt gets floaty, the tanks CoG moves from about the middle to far enough forward where the tanks hang vertically. You have to compensate for this while diving which is why I laugh at the idiots that are all about millimeter precision with weight placement for trim. I'm sorry, but you take a leak while diving and it moves your CoG, every breath of air you take changes your CoG because it moves the tanks CoG incrementally forward with each breath, every foot you descent or ascent the wetsuit changes it's CoG based on depth compensition. Every time your hands move, you are changing the CoG by quite a bit, so precision placement of weight is just trying to compensate for poor diver skill. Now, that being said, there are things that will throw you for a loop. Doubles placed too high on the back, in a drysuit, with neutrally buoyant fins. You will flip over on your head, that is a massive amount of offset weight that you can't compensate for without kicking. Sidemount or CCR diving in a wetsuit with Hollis F1 bat fins, or even Jet Fins that are negative enough to cause you to have trim problems. Those are very real, but those fins have a 2-3lb negative buoyancy at the end of your feet, and sidemount and CCR have a much lower CoG than backmount diving, so a shift of that much weight isn't something you can compensate for. That's why you see many of the wetsuit divers with OMS Slipstreams, Dive Rite, Quattro's, etc. In backmount singles which is what we are talking about, there should be no need for trim weights of any kind unless you have fins that are very heavy, i.e. F1's/Jet fins, in which case those are actually trim weights, whether you think of them like that or not.
Diving is a dynamic activity and your body can automatically compensate for incredible variations in the environment, but you have to learn how to do it, and that can only be done by hours underwater, preferably in a pool sitting around in 3 feet of water, just hovering, doing flat turns, and backing up. Only then will you learn how to compensate properly. If you really want to get your sh!t together, go find one of the GUE people and either take Fundies, or befriend one of them and let them help you. Most dive shops and instructors don't know jack about how to distribute a rig properly, how to properly position it, etc etc. It's not very difficult, but you have to know what you're doing.
