I had this Graupner propeller holder that I modified a lot, removing the cone, and cutting out everything not necessary to maintain the blades on the motor shaft. Also the holder shaft was shortened too.
Made this cone to fit a pusher position on a SkySurfer X8. It covers the holder and reaches the motor body to make a smooth aerodynamical compound.
EDIT 2 Feb 2019 :
The folding prop may be folding down too much at low speed, giving a hard time to the motor balance when starting up again.
The v2 version includes a sort of small propeller on witch the folding prop will bump so that it can not fold down too much.
EDIT 14 March 2019 :
I finally finished tuning up my SkySurfer and its mods. THis ends up in a v3 version of the cone, with a removable plate carrying 2 fingers for the propeller to fold against.
on bricole tout, on touche à tout, et on s'inspire de tout ...