RE: HobbyKing 1/5 50cc Spitfire Mk IX Group Build Tips/Mods
The major changes would be easy to do, this has a wood wing so shortening the ailerons would be easy. It has a wood rudder so pulling the covering off and making the changes would be easy. Not sure about the retractable tail wheel, but if you've made changes to other planes like this I don't think tail wheel changes are a big issue. I think the main changes to the fuselage on that variant are internal along with extra fuel in the wings, that variant does have some nice paint schemes.