We do fly off grass but i didnt have any trouble with mine it left the ground within 15 feet. this was the first flight on the birdy and engine not sure on the size of his tires but they r bigger than mine i think they r like 2 3/4 inch he has plenty of AOA the last prop he tried was a 11x7. Do you think it could be a reverse rotation engine? I started my OS counter clockwise the .52 would start but wouldnt run past half throttle I switched the wires on my starter it started and run so i dont know what the deal is.