Super11XP,
If the only reason for which you want to sell your Champ is because of the performance, there are a few things which you can easily do to correct this.
1/ Improve the pitch control by cutting off the stabilizer just outboard of the outboard hinge and weld the parts onto the elevator.
2/ Improve the directional stability by adding the Aeronca fin leading edge extension. This is a bolt on part and a little fabric work.
3/ Increase the wing span as Turbobeaver has suggested. I've done this on a certified 7GCB with a field approval. This also greatly improves aileron response.
4/ Install larger diameter tires. They don't need to be large "bush" tires.
5/ Install a Citabria seaplane prop 80-46. More diameter than 80" will reduce cruise speed with minimal take off/climb improvement. I've tried this.
6/ This is a little more work but would definitely be the ticket. Install flaps. These would be my preference:
http://www.performancestol.com/products.htm At the very least a 7GCB or 7GCBC (they are the same) installation would do.
After you complete steps 1 thru 6 you will be removing the "For Sale" sign.
In recent times I have looked at some of the fields which I have flown in and out of with my modified 7GCB. I can't believe that even a Cub would be able to use those fields. I miss that plane, what a joy to fly.