I don't even know how mine got switched when I was installing the DX6 but I ran onto that exact problem. I don't figure installation should be that much difference between 6/7. I hope the boy gets it...been driving him nuts.
ORIGINAL: outtamyway
Disregard, Crash already pointed this out...
Lookyj,
You still have your elev and pitch servos reversed. The back servo that is on the other side of the boom from your tail rotor blade should be plugged into the Aileron Channel on the receiver. The servo on the same side as the tail rotor blade is the pitch. Swapping these will fix your problems.