I don't know the rating numbers for your new motor, but I have a YS .91 which turns an APC 15x6 at 9750 RPM. I am spinning it a little fast, but it has great performance. I may try a APC 15x8 to see if that will slow the RPM's down to around 9300 RPM, plus should give more thrust. YS makes a little extra HP compared to other engines in the same class, so you may want to go with a 15X4, 14x8 or 14x6. I had a APC 14x6 which I turned over 11000 RPM with. WAY TOO FAST!!!, but you just have to get several props to find out which is best for you and your style of flying. If you want speed, go with a lower diameter and a higher pitch. If you want more thrust, then go with a higher diameter and lower pitch. The choice is yours depending on your style of flying.