More than likely, the problems you are seeing with the two converted tailwheel trainers you are talking about are being caused by the main gear not being in the correct position. As far as not taking off properly because of a flat bottom airfoil, that has nothing to do with it. My LT40 has been in tailwheel configuration since day one, and I have never had any take off, or any other ground handling problems with it. The key to getting the thing to perform correctly is to get the main gear in the right place. If it's placed too far forward, or too far to the rear, yeah, it will handle like a nightmare. My gear is placed directly behind former #2 (I think this is the number for the former that is directly in from of the wing leading edge). I epoxied a 3 1/8" square piece of 1/8" birch aircraft ply on the fuselage floor, right behind the former, for reinforcement. My main gear is positioned so that the main wheels are just in front of the wing leading edge when the aircraft is sitting in a three point stance, and the wheels are DIRECTLY under the leading edge when it's up on the mains. If the owners of the planes you have mentioned would check their gear positioning and get them mounted correctly, I think the problems you have seen would disappear.