I know it has been a common practice to have dual receivers in larger, more expensive planes for redundancy and power distribution.

As for the Chris' problem, it sounds like you need to have matching receivers to do so for the Spektrum systems. Contact Spektrum/Horizon and see what they say.

Since every full range Spektrum receiver has at least two receivers to begin with (main and at least one remote), and you can get the AR9100 which actually has four receivers (main and three remotes) and two battery inputs, trying to bind two separate Spektrum receivers may not be the best way to go anymore.