To do nice KE loop, you will need to maintain speed for 1st quadrant while having enough thrust for 2nd quadrant. 4" pitch won't work too well. .91 FS (the 4-stroke) may not have enough power. My UCD w/ Saito 100 using APC 15x6 has just enough power for nice, large, round, and most importantly, even speed, KE loop.