cra2:
More than likely, most of my rec diving would be with singles.
When you refer to channel depth being a factor, what exactly are you talking about? I have been told NOT to do the BP/Wings setup because "the plates are not made for singles and you'll have to buy an adapter and/or the single will stuck up high in the middle put you off-balance easily."
Plates are fine for singles or doubles ... whoever told you that plates will make you unstable simply don't know what they're talking about. Truth is I feel far more stable in a plate than I ever did in a BCD, and I've only, so far, used mine for singles.
Whether or not you need a single-tank adapter will depend on both the wing you choose and the plate you choose. Some plates have slots cut into them to accommodate tank straps ... others do not. If you choose a plate with strap slots, and you don't want to use an STA, you'll still need a way to stabilize the cylinder. Halcyon builds a wing that has metal rods built in for this purpose. I don't know of any other wing that comes with this feature.
The channel is the center portion of a plate. If you look at a plate, it is shaped to accommodate your back. Running vertically down the center is a recessed "channel". This part of the plate is recessed to accommodate the screws that hold the backplate and wing together (and single-tank adapter if you're using one). The shape of the plate and depth of the channel does vary from one manufacturer to another. What that really means, to the single-tank user, is that you have to pay attention to the type of single-tank adapter you use for the rig you are putting together.
The backplate/wing system is very modular ... you can basically mix and match plate, wing, and STA from any manufacturer. If you're planning to dive singles, you'll want a wing that's "donut" shaped. Halcyon, Oxycheq, and DiveRite build such wings. Others may, but those are the ones I have used and can recommend. Doubles wings are more horseshoe shaped, and are wider to accommodate two cylinders. Avoid purchasing a wing that claims to be good for both ... as it order to accommodate both they need to design the wing with compromises that make it ideal for neither.
Harnesses also vary quite a lot. The traditional harness is a single piece of 2" webbing that runs through slots to comprise the shoulder and waist straps. This is the style of harness DIR requires. Non-DIR harnesses run in a variety of configurations ... the most popular being a three-piece harness (like the one shown in the link provided previously in this thread) that function more like a traditional BCD harness. These are not DIR compliant. They have some advantages in terms of convenience and comfort, but the tradeoff is increased cost and complexity.
Some harnesses accommodate integrated weight systems, others do not.
Hope that helps clarify ...
... Bob (Grateful Diver)
