RE: kelly f1 with YS63
My Kelly is also powered by the ys63 and have settled for a APC 12x7 for now but I have also tried the APC 11x8 and 11x9. The 11x8 is probably the fastest but the rpm went to high for me to be comfortable with a fourstroke but the 11x9 is probably safe. Using 20% nitro and APC 12x7 turning around 10700rpm rich static the plane will pull straight vertical after the take off and onloads in a dive and have good speed.