Erich,
I like my Halycon wings and I prefer my STA to be one pc, not 2. I ESPECIALLY like Scott Koplins weighted STA - by using that I can get another 4# off your belt. I have a Halcyon STA now, bu I'd go the Koplin next time.
Rumor has it that the BEST way is to use a single wing (for Halcyon thats the Pioneer wing) for single tanks and a bigger wing (Explorer for Halcyon) for twins.
Most guys dive a 27 or 36# wing for singles - some a 45#. I have a 45# as I didn't think the extra life would hurt me. Based on another posting I saw today on this board by another diver who has a 45# wing also - he isn't experiencing any problems from have a 45# instead of a 36# wing.
Most wings for twins are like 55# and bigger up to 100# lift.
I have heard of some guys using wings meant for doubles with a single Al80 tank. Some OMS guys do this and use something called a 'Spreader Plate' to keep the larger wings from 'flapping' around being they were meant for twins and not a single AL80. I personally don't know much about that - but I have read postings from others on it here also - Pro's and Con's.
Dive Rite makes good wings too, I hear. I hear both good and bad on OMS gear. Like anyhting, EACH brand will have its local patriots, just like Ford and Chevy owners! YOU choose!
I hear that Halcyon wings are built with better and stronger Cordura. I don't know myself. I DO know that Halcyon makes their inflator hose the proper length so its not hanging down to your waist. But, one could shorten the OMS corragated hose if they wanted.
Good luck!