May be the paint ! No really the only thing I have done different is put the RX inside the fus' just behind centre of gravity , As for flying if I put a slightly smaller battery in ie 1.8 3 cell it goes tail heavy and is a pig to fly, the difference with the batteries is 1oz/25gms !! that's how touchy it is
The paint is from "RANGE" Artists water based spray paint the grey is Tamiya acrylic water based model paint
Think these are sold at Hobby Craft shops as well, I have done the under side with black and yellow stripes to aid orientation. ( I'll add a picture)