I lack the ground clearance for a 12x4. The tips would be so close to the ground that I'd need a paved runway to take off AND I'd have to grease every landing lest I bump the tips into the tarmac. Even a mildly rough landing would compress the springy front gear enough to give a nice prop strike.

If I change props it's going to be to a 10x5 three blade, for two reasons. One: I like the looks of three blades better, and two: It will give me better ground clearance without sacrificing any performance. The 11x5 came with the plane, it will be used until I'm good at flying. Or until I break it on a rough landing, whichever comes first.

Thrust calcs put me at a flying speed of about 65MPH, seven pounds of thrust and 1.1HP, more than adequate to learn to fly with.

Also, I'm ~850 feet above sea level.