RE: What parts did you use to build your CMP P-51 140? (Build thread)
The first time I had the tailwheel retract in I had to use a 1-1/4 inch tailwheel and I didn't think the retract had enough range of motion to it. I made a few more mods to it, increasing overall range of motion by about a half inch, and can now use a 1-1/2 inch tailwheel. In the down position there is a two inch clearance under the scoop and the tail is a whole half inch higher up off the ground. This will help some when flying off grass strips.
Attached is a picture showing the gear test-fitted and good ground clearance.