The Halcyon probably will not fit the Dive Rte plate, but you can always jury-rig something. I used one of those pads - a de-stickered OMS pad on my Abyss backplate.
You know, the plate itself is pretty comfortable as is, plus it was a royal pain pulling my DSMB out from under it.
I went back to my Dive Rite sleeve and ditched the pad. I do use Tobin's delrin starwheels to hold my tanks to the plate - I got gnawed a couple of times by the wing nuts diving without a wetsuit.
Nice big thigh pockets are the best thing for these things, although the new version of the Dive Rite pouch is better than the old one I have to deal with. It keeps it stored, but you can get it out without jumping through a bunch of flaming hoops. I keep my spool clipped off back there. You gotta practice with whatever you rig though, so when you do it for real, it works AND you look cool doing it.
Hey Stephen Ash, for a guy in a landlocked state chock FULL of galoots in bigarsed cowboy hats with rifles in the the windows of their pickup trucks who talk real s l o w, you have some good gouge on this stuff.
You must be in the Witness Protection Program or some arcane form of desert exile, but don't worry - I'll never tell...