Let the ailerons go to the tip... this is an aerobatic plane not a racer... I don't agree that the outboard part of the aileron doesn't do anything. The roll induced angle of attack will be the greatest at the tip and any fixed trailing edge there will induce a stall which will decrease roll rate. The aileron at the tip may not be helping to roll the airplane but it is getting out of the way to prevent the tip from stalling (aileron deflection reduces the effective angle of attack). If you want to get rid of some useless aileron start at the root where it has no moment to work with. The only reason to have ailerons at the root is for hovering.

Ty

P.S. the airplane in the picture behind me is my Pitts S1S with an early version of the Ultimate wing... this version only had half span ailerons and used tip plates. It rolls just as fast as the ones with full span ailerons.