Carlos,
Sorry I didn't check this thread sooner. I am almost sure that you have to use channel 6 for flaps. Don't think 6 will work right for ailerons. The airbrake function assumes flaps master is 6 and ailerons master is 1. I don't know what problem there might be using 5 for the second aileron. The radio has a built in feature for second aileron and it is selectable between chan 7 or 5. Since there is no question chan 7 works, use 1 & 7 for ailerons, 6 & 5 for flaps. That is what I used.

If memory serves me, I simply did a p mix with 6 master, 5 slave on some switch (d i think. doesn't matter except not G) for flaps. Then flaperons on, flap trim on, set to 0, then use the built in airbrake function to set that up. I think I had to do a second mix of chan 6 to 5 on all the time for the flap part of the airbrake to work.

I had a lot of fun with my ultastick before a case of dumb thumb turned it into matchsticks.

Jim