I've been doing some prop tests on a newly purchased .75 and found a couple of good performers.

The new line of Evolution reinforced nylon props looked good and I found the 14x6 worked good. A Zinger 13x7 did as well. Both were 2bladers and you asked specifically about 3bladers. I tried two so far and one gave less performance than the two good 2bladers. Basically, the reason for the poor performance with the one was because it wasn't enough load on the engine. The rpm was the highest the engine has shown with any prop I've tested on it so far. The poor performer was a 12x6(3) that turned over 12,500rpm on the ground.

The best prop so far on the .75 on that airplane has been a Master Airscrew 12x8(3). The engine turns the least rpm on the ground of any tested so far, but it pulls like a bull in the air. It's what I've flown on the plane since trying it. And I've not been much interested in more prop tests since testing it. The engine turned it just over 9,100 rpm on a 90+degree, low pressure day. I haven't bothered to tach it since the test day.