I am driving since some weeks also with a cone behind my FR Propeller but at moment without the blades. I got 10-15 minutes more time for foiling.
Next step is to print a cone with the blades.
I mount it total easy, the FR Propeller is mounted with a M8 screw. Behind that you gave around 6mm free thread. In my 3D printed cone you can easy put screw inside.