Ok Squabbler,
First question I have is, Are you flying a Flip 3D? With 60 plus degrees of elevator throw at 150mm CG, mine will not snap on any elevator input. How much does your plane weigh? Are your elevators symetricly coupled by the bellcrank? Are your Flap and Aileron endpoints giving an equal aileron throw up and down left and right? Do you have any rudder or elevator to aileron mixes active? Is your rudder or ailerons mechanically trimmed with a lot of bias?

As far as the 8103 mix is concerned. The ailerons will start movement at about 75 - 80% of elevator (you have the rest of it correct) deflection and complete their movement to 100% by 100% of elevator deflection. This can be accomplished on either Mix 1 or Mix 2. I would assign this mix to the Prog Mix switch at the top right rear of the radio. Here is how it reads right off of my radio.

[Prog Mix 1]
ELEV+FLAP
Point - L = 100
- 1 = 0
- 2 = 0
- 3 = 0
- H = -100
SW:
MIX

I put all my other KE rudder mixes on Mix 3 and 4 as on always so They work linearly all the time. They seem to be needed in all rudder moves anyway.

Your snapping concerns me though. This may also cause your wings to rock more than normally as well.