I had the same problem and I dont like Y-harnesses. My harrier46 and UCD 46 both have mpi on board glow(uses channel 5)

Heres what I did
channel
1&6 ailerons
2&7 elevator
3 throttle
4 rudder
5 on board glow.
reciever a futaba R127D (7 channel)

with an 8 channel its much easier just use 2 and 8.

Heres how I did it with the 7 channel via a mix on my 9C [link=http://www.futaba-rc.com/faq/faq-9c-q512.html]dual elevator servo fix[/link]

You may can do the same with the 6 ex? goodluck, SD