If memory serves me correctly I do not believe that a 12 inch prop is an option without cutting some sort of channel. When Mr. Mikulasco (spelling) designed the dedicated land version (enforcer) he turned the engine around and designed a long channel cutout in the wing for the prop. So Joe if you do go with a sixty This is one of the few times you will ever hear me suggesting a three blade would be useful.
In the meantime getting the mains footprint just a tad forward and closer to the Cg will give you more pitch authority sooner.
John