I HAVE A GP BIPE WITH A SAITO 72 ON IT. THINKING IT WEIGHS IN AT ABOUT 6- 6 1/2 POUNDS. USING AN APC 13X6 NOW AND IT FLYS WELL BUT WONT BLAST OFF VERTICAL. HAVE A 14X4 PROP BUT HAVNT TRIED IT YET, NOT SURE ABOUT MAKING ENOUIGH SPEED WITH IT. I CAN GET IT INTO A HOVER BUT MY THUMBS PROBABLY DONT FLY WELL ENOUGH TO KEEP IT IN ONE. NEEDS ABOUT 75-90 PERCENT THROTTLE TO KEEP NOSE UP DEPENDING ON WIND CONDITIONS. IT WILL GO UP VERTICLAL WITH FULL POWER OUT OF STALL BUT WILL NOT CONTINUE STRAIGHT UP. THINKING ABOUT A SAITO 91 IN ITS PLACE, THAT SHOULD SOLVE ANY WEIGHT, DRAG, NO ENOUGH JUICE PROBLEM.....