I use a 12x5 on a 46AX. I also was used to using a lower prop and used to the high rpm's, but learned quickly that I don't need to be spinning at 13000+ rpm, now I like the sound of the lower rpm, and my plane is flying better and the engine seems happier/not over revved.

The 55 should be swinging 12,13 and maybe even 14" props.