I think that is the 6XA or 6XH. Its a computer radio but I am not sure if it has mixing for dual elevators. I think it might but I cannot remember for sure. looking on the futaba site it does have mixing, it will just depend on whether or not you can use channel 5 in a p mix. Are you using seprate channels for you ailerons?

You know, something else you can do is simply rig up for a single elevator servo if you must. You just place in near the rudder servo and run a pushrod back to both elevator halves. We do it on pattern planes all the time. www.centralhobbies.com sells a nice lightweight systems called DEPS (Dual Elevator Pushrod System).