For those of us that use a 6s setup with larger props and the RVJET, we have to mount the motor further back to avoid hitting the vertical stabs. Even after doing this there is a chance on start up that the blades lurch far enough forward to hit the vertical stabs. I have made a simple prop bumper to help stop this from happening. It mounts between the prop holder and the spinner base. You may have to modify the spinner prop cutouts about 3mm for the additional space the bumper takes up. I am sure this can be easily modified for other spinner/prop adapters. The pics of mine are not finished of yet so it looks a little raw.Made with 1.75 abs on a solidoodle press extruder 250c bed 110c