Hi,

13x6 is the benchmark prop with the .62

I hear that the Saito .56 is the most suitable for the four star, but Saito recently released the .62 and the weight and size is almost identical. The .62 can swing the same props at 1,000rpm more than the .56 but the 12x6 can exeed the max revs of 11,500.
The .62 can get the same rpms as the .56 swinging a 1" larger prop .

I got the .62 because i will probably be a more versitile engine on any future planes.

If you believe Bolly's marketing blurb, you can run a 1/2 larger bolly and use less HP because they are more effecient.