Dave-

You may need to get a different insert. I have a Hobbico starter. It works fine with a large plastic spinner. Reversed, it works fine with just a prop nut. When I tried to use it on a "heavy hub" spinner nut, neither way will work. It is too big the normal way and won't grip it the other way. I bought a Sullivan replacement hub at my LHS that works great. I think it is for "medium" size spinners.

-Scott