I am having difficulty fitting plastic spinners (specifically a DuBro 2" spinner)) to my electric motors. On the motors I use, the prop is attached using a collect that is locked down when the prop shaft nut is tightened. However, the threaded shaft extending from the collect is not long enough to accommodate both the spinner backplate and the prop hub. If you know of a solution, I would appreciate hearing it. I am building a Phil Kraft Flea Fli from plans and I need the spinner look.
Thanks.

Try to reduce the washers thickness, also dremmel out the prop hub if it's thick and safe to do so. I had to do the same on few props to suit various motors even with out spinners I always try to eliminate for better models performance. (Unless a serious scale model)

As on this pic.