The sweep back of the 25% chord line and the tapered planform both promote tip stall. Unless you are prepared to investigate the stall angle of attack of various airfoils via X-Foil, I suggest that you fly the Giles with plenty of stall margin during the landing approach. Even if it involves comming in very hot. A better alternative might be to modify the Giles with inboard flaps for landing. Deployed inboard flaps will generally prevent tip stall on landing approach.