G'day Dick,
How's it going, I have 2 elevator servos mixed with my DX7, in fact I am using it with the 3 planes I use with my DX7, easy to do, & no need for "Y" leads or reversers or whatever, just plug right Elev servo into elevator channel & the other into Aux2, & mix them, using either mix 5 or 6, trim include mixes, you will need to INH, the flap switch & slider, check out Bob's DX7 page for any hints you may need, but it is the best & simplest way, & you have full control over each servo.
Keep em flying Dick.