I used a 12.5 inch on my Saito .56 on a Somethin' Extra and there was just enough room to fly it from a grass runway. Funny thing was, anytime the tail wheel would come off the engine would stop because it was hitting the grass. Anything other than a perfect 3 pointer killed it too...Sure taught me how to land the thing!

A 12.25 inch is better and there should not be any problem with a 12 inch.