ORIGINAL: aspeed
They are using the APC electric 4.75-4.75'' prop for the mouse race reedy motors. They would likely burst in your face on a TD or better. Apparently they are faster and give more laps than more conventional props. Maybe a fiberglass copy would be ok for a TD or Norvel or even Fora for a speed plane.
The aforementioned Caliente made a big jump in speed when Jeremy switched to APC electric props and rotated the cylinder to be in front of the wing fillet. He and I talked about it on the phone while he was building the 2nd Caliente and I was happy the suggestions worked.
APC offers a lot of choices in 4 and 5" props, enough that just about any 1/2 engine can be made to work where it is at it's best.