ORIGINAL: ADChobbystore
If you are using a 9x7 now, and the power is acceptable, but you are looking for a little more top speed, something around a 7x7, 7x8, 8x7 would be the range I would look at. Going all the way down to something like a 5x4 is going to give you next to nothing in terms of overall power.
THANKS SO MUCH FOR THE INFORMATION ON THER PROP SIZES .AS I GAIN IN TOP SPEED CAN I THROTTLE DOWN AT TIMES AND GET THE SAME DURATION OR MORE WITH THE SMALLER PROPS? I HAVE HAD EXPERIANCED THE BRUSHED TYPE SPEED 400S BUT NOT THIS NEW BRUSHLESS I HAVE NOW WHICH I REALLY LIKE.