+1 on the recommendation to strengthen the tail wheel mount. Lite ply at a minimum, and a small piece of hardwood, spruce, or basswood may be better. You will probably need to chisel out a recess for the new wood. An alternative seen on this thread is to install blind nuts from the inside backed up to a piece of light ply, and then to use bolt to hold the tail gear in place. That of course requires that you are comfortable cutting and repairing the covering in the tail. The balsa back there is really soft, and if you land on grass, your tail wheel is certain to tear out, even with good landings.