Thanks for all the info! I picked up a dive rite classic with a Ss back plate for &100. It had the back pad, weight pockets, I just had to buy about $130 of things like new webbing and shoulder pads. For a single tank would you recommend getting a horseshoe or donut?
Nice find! A new stainless backplate by itself runs about $100, so call anything else you picked up along the way a win. I agree that the back pad and shoulder pad add little value; try diving it without and I think you'll agree. If your Dive Rite Classic has no leaks, you should have no problem selling it at a profit -- I see a used one on eBay right now for $90 + shipping.
Dive Gear Express has a nice
article that illustrates the taco problem. Basically, the bigger the wing is, the more annoying it is to trim out and manage the air bubble inside of it. Not to mention the increased drag. Honestly, any single-tank wing in the ~30 lb range should do you fine, the differences between them are small. But if you're choosing between a horseshoe-shaped one and a donut-shaped one, go for the donut.
Why do tech wings not have as many dump valves than normal rec BCD’s?
Every extra part adds cost. And worse, every extra part, and especially moving parts, will eventually fail. When a dump valve fails, you may be in a position where you need to complete your dive with a useless, empty wing. If you're in open water and weighted correctly, you should be able to just swim up. If you're in an overhead environment or have a mandatory deco stop (so a tech dive), simply swimming directly up is not an option.
I think you will find that the overriding philosophy on all tech gear is to eliminate extraneous parts wherever possible. This is because each extra potential point of failure increases both the stakes and the likelihood of a serious problem, so that extra risk had better be buying you something good. The standard tech / Hogarthian wing setup has only the 2 most useful dump valves -- one on the inflator for vertical trim, one on the butt for horizontal trim. If there were a really good reason for additional dump valves, people would probably use them, but there just isn't one, so they don't.
By the way, you might want to think seriously about what
@tbone1004 is saying about 7mm farmer john type wetsuits. If you have never tried it before, you might want to simulate a wing / BC failure and see if you are strong enough to deal with it. You can try this by going down to whatever is the deepest depth you normally dive at. Find an empty spot on the hard bottom where you won't hurt any flora and fauna, and then completely empty your wing / BC. You want to be able to swim upward. If you cannot do this, then you should consider how you would handle the situation of a punctured wing / BC. Perhaps your solution would be to dump weight, which would indeed get you off the bottom, but you would have no way of controlling your ascent, so might end up in a very dangerous situation in the last 20-30 feet.
The point of this test is not necessarily to make it all the way to the surface, so you don't need to actually dump your weight and do a buoyant ascent. If you're able to swim up, say, 10 or 20 feet, then your wetsuit will increase in buoyancy which will help you to ascend. So with some pre-planning, you can try this with a buddy on a normal deeper dive, verify whether you're able to swim up from the bottom or not, and then continue to enjoy your dive.
Best of luck, I think you're on the right track here. Edit: I should add that I'm not a tech diver, but I do use a backplate + wing setup on rec dives, and quite enjoy it.