Extraslim,

With an 11x4 you will still be under-propping.

If you are destined for fun-fly, an 11.5x4, or a 12x3.75 would serve you better.

Do make sure you make the fuel lines as short as possible and the tank as close as possible to the engine. The HP is not known to be a very good sucker.

If the plane is a tail-wheel fun-fly, adjust the idle mixture at runway attitude; three point stance with the nose up. Also make it a bit richer for this purpose.

There is a usable range of adjustments, not just a single point.

Sincerely,