Ok, to start, i am a recreational diver myself so i'll give you the setup i use.
First, i use the Stainless Steel backplate, because it is about 6lbs neg, that allows you to drop some weight off your belt(ABS System). Halcyon has an Alum backplate but it cost just the same and you dont get the weight benefit.
Then i bought the 36# wing, i went with that becasue it was the biggest they had for the single tank setup. the 27# is teh next one down but it cost teh same.
The Harness came with the backplate and is teh standard harness that comes with Halcyon. It does have a wide crouch strap which is nice cause it doesn't ride up..
Now the weight system, the weight system comes in two flavors, 10lbs and 15 lbs. That means 10 on each side or 15 on each side. Of course you can fill it with as much as you need up to 10 or 15 ibs. the bags attach to the lower end of the backplate and have a slot for the webbing harness to slide thru. The weight bags sldie into the pouch and have a release buckle that snaps closed.
this makes the bag impossable to lose and easy to drop. Note, the 15lbs is setup to allow the attachment of a Can Light (HID) very cool option.
Now, of coruse i dive DIR so i also have a hose config that is differnet then the standards of most cert agencies. But that wasn't your question so i wont preach about the benefits of DIR.
However if you are interested, ask away or email me.
Good Luck and stay wet