I’m leaning towards the backplate wing setup, but I’m not sure if I should go for the steel. In class I was completely neutral with their equipment without weight in rash guard and shorts. I’m down 30 lbs of fat since then so I’m possibly negative. If I let out half of my breath I can sit on the bottom of my pool. Would the steel possibly be too much weight?
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I ordered the deep six 3 mil suit that was recommended here.
It's possible that the steel plate would be too dense, depends mainly on the exposure suit and tanks you're running. But most times, steel is the way to go. As one point of reference, I'm 5'11, 160 lbs, just a bit positively buoyant, and I wore the size M Deep6 3mm in warm salt water earlier this year with my steel plate and rented AL80 tanks. With no lead at all, I was buoyant in shallow water with a near-empty tank, so slapped 4 pounds of lead in the weight pockets and was good to go for the whole week.
High pressure steel 100cf tanks like the ones I dove at home are roughly 5 pounds more negative than AL80s, so I would have been set with no lead. If you dive some low pressure steels, I'd consult a chart like this one to see if they are substantially more negative than a typical PST-100, and if so go for the aluminum plate. In the end, if you end up wanting a different plate, keep in mind that they only run about $80, and are pretty much interchangeable between different brands.
Edit: Oh yeah, and I should have mentioned. You already have a point of reference for total ballast with whatever gear you took the class in. Steel plates are about 6 lbs negative, aluminum plates about 2 lbs negative. So if you needed 6 or more pounds lead, then a steel plate would have been just fine for that setup. The fact that you've lost weight since then, and are probably looking at a less buoyant BCD might knock a pound or two off. Also, not sure what exposure gear you had for the class, but if it was some other 3mm full suit, then the buoyancy will be similar to the D6. Clear as mud?