Right on about the 12.25x3.75

I tried several props (not the 12x4) on the 46LA and the 12.25 works great.

My .46FX (with tower muffler) hated the 12.25 but loved the 11.5x4 APC, much more thrust eventhough it is smaller. The smaller prop on the FX reved up significantly higher than the 12.25 inch prop, the increase in rpm more than offset the smaller diameter.

Bottom line is you just have to experiment and find the right prop for your engine and style of flying.

Inorris:

You're right the LA is spinning around 11K and making only .6hp but the thrust is greater eventhough I'm off of the power curve. Go figure