CeeGee,
I use the Futaba 9C radio. I really like the radio but find it a little hard to program. One nice feature though, when you do get it programed correctly you can save the setup to your next model and not have to program it again. You then only have to "trim out" or maybe change one or two items.

You do not need the Y harness. I think the extra elevator is channel 7. Then you just activate channel 7 and you're good to go. You'll have to watch the rate and end points so the elevator halves move at the same speed and end at the same place. If you need it I can post all the channels for the UCD46 tonight when I get home and can look at my notes. Also, I would pull the wire out of your wings. It may actually cause a balance problem. Just zip tie the extra together and store it in the center of the plane. Also, I think you might have a prop balance problem. All the UCDs make a "druming" sound and it is nothing to worry about. I've flown them a lot and I've never had a problem with structrue. They do make noise but it is not distructive. But yours sounds excessive. I would be very care to rebalance your prop. I'll bet you find it off a little bit. With a perfectly balanced prop and the wire tied up snugly you'll find the noise isn't too bad.
Thanks,
Barry