RG 15A 8.9% 160mm cord…. that should cut the air nicely no?
http://www.ae.illinois.edu/m-selig/ads/afplots/rg15.gif
thick enough to fit in some 8g servos. If one servos per aileron was not strong enough, could always put a second one.

That should make it a nice slope soarer… UK is the right place for that 🙂

Finding a used fuselage from a high performance glider could minimise the work…