I am running an 11x5 on an OS 46AX. And it will will do well vertically. I would not say its totally unlimited on my Avistar, but it will drag it up. And I am running rich. If I had it leaned out, it might be unlimited. An 11x4 works well too. I don't know how much ground clearance you have have but with my Avistar and a larger front landing gear, I am still mowing grass with an #11 prop. I guess you could bend the main gear and extend the front in order to put a 12x4 on it. But I am nose high as it is and can't run a #12 prop.