Not very much, my sheeting process makes for a very strong bond between the foam and balsa. Granted if it weren't for the struts that will connect the wings they would most likely fail. I have always thought that we build our models way stronger then need be in most cases. Typically we build our models to survive transportation/handling and to survive the occasional bad landing. The last airplane I designed was for warbird pylon racing. 62" span, glass fuse, balsa sheeted foam wing, all paint. Complete with retracts, 6 servos and a YS 115 it tips the scales at 6.25 lbs. Note how thin the wing is.