The PT40 is an excellent trainer platform and the issues you described can be fixed. The Park Flyers you listed are not very forgiving for errors made in flight and not near as as stable platform as the PT40. Stay with the PT and fix the minor issues. 1 pound of weight aft seems to be a bit much. Are you sure that you are balancing from the correct CG location? I can't believe it would be that far off unless you added about a half a pound up front.