Actually, Dave, the answer is a little more complex than what you have gotten so far.
The ricochet potential of a pellet hitting a spinner depends on the relation between pellet energy and paddle weight. In the case of a pellet hitting the apertures between plates, the possibility of a pass-through either of the complete pellet or of debris, depends on top of the weight of the plates, on the quality of the manufacturing and the closeness of the fitting.
Tony G is absolutely right in his appreciation, but I feel not enough emphasis was placed on the 6 ft-lbs energy level he shoots at.
If you shoot at anything higher than 6 ft-lbs and you are concerned about where the pellet debris is going to fall, or about what happens when you hit the division between 2 or 3 plates, then you really need a much heavier and better constructed spinner. A heavier / larger paddle, better fit to the adjoining ones, will effectively halt the pellet and let the debris fall to the sides or down with much less chance of the pellet debris flying up and beyond the spinner's location.
If you want a REALLY GOOD spinner for a little more money than the "light plinker" version, get in contact with Dave Kasinsky at Metal Spinning Targets:
http://www.metaltargets.com/SpinningTargets.htm
But again, this is ONLY in case you are shooting at energy levels above the 6 ft-lbs of Pentagon F guns.
HTH
Un Abrazo!
Héctor