I would make two changes to the stock wing. First, get rid of the washout. Then ditch the stock tip airfoil. I would reduce the tip thickness by 2% or 3%, move the high point forward 5% and increase the leading edge radius. IMO these steps would make it a more enjoyable airplane. You could even get a bit crazy and anhedral the stab. That has the potential to decrease the rudder/aileron control couple.