I got (as a gift ) an Enya .80-4C in a Pica 1/5 scale Aeronca Sedan, which weighed in at about 12.5 lbs.
It would fly it in a scale like manner...
It had a 14X6 on it when I got it, and that wound up being the best prop for that situation. I tried an APC 15X4W which improved take-off and climb performance, but I had to keep a higher power setting @ cruise...(as you could imagine )
Both of the above props would turn about the same r.p.m. of around 8,700 on 10% Powermaster.