ORIGINAL: iron eagel
If I can spin a 13X10 prop with that perhaps a 12X12 might work, will be interesting trying to prop this thing. Another option is to go to a smaller diameter 3 blade while they produce less thrust they come into there own as you go to higher speeds.
I guess you won't know until you try but there is going to be a lot of potential 'P' factor with a 12-13" prop. It may want to torque a bunch on launch with short coupled verticals. I'd make arrangements for right thrust.