After wading through all this, I still wonder why two CM15As can not be used with each other? They are polite so should not trample each other...
Dave, I still do belive they can be done, but the only thing that you might have a problem with is when you want to dim or brighten a light. Instead of the light being dimmed 1 level, it might go up 2 levels (from one brighten button push) because both trancievers are sending the same code. It'd be best to turn on of the unit's trancievers off; then you should not have a problem at all. This what I was going to do but found a better way with better RF reception per my post above.