Will my Eclipse 7 support a dual elevator servo setup?

Only if your particular transmtter is one of the few in USA which has the "AILV" function.
Previous answers to similar question:
Hitec Eclipse - Dual Elevator Servos (1st link changed to this ).
Dual elevator servos (AILV = Ailevator) - Optic 6
E.P.A - A.T.V - Dual Rates differences, cautions and arming ESC may also assist.
Further information available under "Giant Scale, Large RC models, Twins & Multi Engines" and "Radio Systems, Accessories, Alterations and FAQ" on my web page.
Regards
Alan T.
Alan's Hobby, Model & RC FAQ Web Links

So what do I need to buy in order to make it work and where do I buy it from?

I knew I should have bought a Futaba 9cap. [>:]


For Sale: Hitec Eclipse 7 perfect shape.