@67macoshark
Individual buoyancy is a tough one, and is only a factor in making sure you choose the right plate material.
Those that are very negative typically require more exposure protection due to lack of body fat for insulation, but -5 is very rare, most people that "sink" are still only a pound or two negative. When you are diving in salt water that will usually get back to very close to neutral, and a 3mm shorty is usually enough to get that number to 0 in salt water. That is certainly a factor that you need to take into consideration if you are very negative though in plate selection. I am slightly negative, but in salt water with no exposure protection and an AL80, a SS plate is about perfect for me. I might be 1-2lbs negative because I use a DSS Long plate which is a little heavier than normal, but it's very very close. An extreme example of that is my brother who has a Kydex plate from DSS and with a LP72 in a 5mm wetsuit, he is still a couple of pounds negative in fresh water. He's about perfect in the salty stuff but he has no body fat on him and a lot of muscle.
Now, for people with lots of bioprene, if you are very positive, then you obviously should choose the steel backplates, but fat does not compress, so it does not need to be "compensated" for since it is a fixed value.
Wings are buoyancy compensation devices, so they are a device, that compensates, for buoyancy changes. In a configured diver, there are three things that need compensated for. Gas volume is #1, suit compression is #2, and anything that you plan to pick up that isn't big enough to justify a lift bag *usually lights, reels, misc stuff like that*. Tobin and I do beg to differ that you should also plan on a bit of a buffer to keep your head, first stage and valves high and dry, so I like to pad my wing size with 10lbs, but that's just me. I never seem to actually do that when ordering wings and my wings always seem to be close to maxed out at the beginning of the dive, but oh well. I don't do a lot of ocean diving, so for flat water stuff it is not a big deal.
So factor all of that in, and a 30lb wing is usually about right for 5/7mm wetsuits in a decently sized single tank *i.e. not a cave filled LP104 in a 7mm farmer john, but perfectly adequate for a 7mm steamer in something like a HP130.
now to
@rgilkes, contrary to what is often said about Tobin, he is quite a nice guy and very helpful, and I'm sure that while he gave you quite a bit of good, and free advice, and you chose not to order a rig from him, he will still answer that question for you. That said the general rule of thumb is 2-3lbs per mm of wetsuit in the salty stuff. Closer to 3 for bigger suits, closer to 2 for smaller suits. You are probably in the closer to 2 range
