I experimented last night and discovered that both the Scotty fly rod holder AND the Scotty spinning/casting rod holder will each hold both spinning AND fly rods.

With the rubber strap in place the fly rod holder holds both types of gear well.

With the sliding ring locked in place on the spinning rod holder, you won't lose your fly rod, since if a fish pulls the butt end out of the holder, the reel will catch on the sliding ring.

In summary, either rod hold CAN be used for both spinning & fly gear. If properly secured, you WILL NOT LOSE YOUR GEAR. Each type of holder has its advantages for the gear it was really designed for, however, and seems just a bit awkward when the other type is used.