RE: Prop Nut: Is there such thing as TOO tight?
Too tight is bad. If the cone of the spinner rubs against the prop, it could cause the prop to wear and fail
(read - "shed a blade") while the engine is running. Nothing about the spinner except the backplate should EVER touch the prop.
After snugging the prop nut down, you shouldn't need more that another half turn at most to hold any prop.
There is only one cause of throwing props - the engine is backfiring and slinging it off. Richen your high speed needle.
Hmmm..."spinner prop nut". Do you have a 2-piece full spinner or just a cone-shaped prop nut?