HorizonHobby.com carries a servo-reversing Y-harness. I don't recall the part number, so you'll have to search for it on the site. It works fine for what your needing, and cost is actually no more then standard Y's(I'm thinking about $10-$12). It even has a finite adjustment pot for fine tuning. I've used a few of these with excellent results. I do think though as Hammbone said, a new transmitter might well be in your future. There's alot of brands of transmitters that will offer that mix within programming. I have the Futaba9C and it does offer that feature, although I have used it both ways for the set-up your talking about. Really either way works just as well. Good luck, you'll do fine.