The original idea was to go for tapered wing...

we changed the plan and went for paralell chord, but with a tapered aileron.

Two reasons for this... first of all to add shape.

Secondly.. it is true that (in my view)

paralell chord ailerons on a fun fly does not work... too much drag at the tip. (i.e. as you say Surrey - harriers etc)
secondly is control response. Ailerons that are too large can have an adverse effect...(unless they are of stiff balsa and have powerful servos)... they can twist and create too much blow back. Narrower tips help allevaite this.

Many of the fun flys today are actually designed to be flown at near stall speed.... maximum throttle control...
In truth many folks also want to hit the gas and do a bit of flying too.... thats when huge ailerons let you down.

We will see how it flies....when the rain stops.... its been absolutely bucketing down here today and tonight !

some more pics

sorry about the quality but outside pics was a no go today !