For the final modification try and get another wing, cut it in half and glue it back together without dihedral. It will be a blast. The only problem in carrying out this mod it to create a new wing spar. What I did was drill into the halves and insert an aluminum rod I bought at the hardware store. I think it was 1/4 inch thick. The rod was epoxied in place and did not add any significant weight to the plane to make a difference. The no-dihedral set up makes it into a very aerobatic plane, not competition level but a lot of fun. If you also increase the size of the rudder it will be even better.

This plane lasted several years and I have to say it was one of the most fun planes to fly I have ever had. It finally died under the wheels of a truck when its engine quit in a very tall grass field and in trying to retrieve it we ran over it.