I have a 40 size , phoenix, strega arf. I am trying to adjust the right amount of flap in the ailerons for a smoother landing. I have a spectrum dx6 and set up the servos so i can dail in some flap.I just dont know how much throw i should start with on the first set up attempt. the ailerons are set at 6mm throw up and 6mm down on hi rates and i took 15 % off on low rates. I have flown the plane a few times and many others but never messed with trying to use flaps. What do you all think.

Try a little at a time. What happens is that if you use too much and you need to steer with ailerons the upward moving aileron dumps the lift and the wing stalls.

5 degrees maybe for starters.

I'm not familiar with that design but if they are wing tip ailerons don't do it, if they are full wing span ailerons you can get away with a little.