Bill,
Thanks for the input - I never actually pitched it while using the spin. The quote was just something somebody told me to reinforce that I should never, ever, release the main sheet when a gust hits - as in it's better to take other consequences than to break the mast (a fellow in our Fleet lost his Mystere 6.0 mast this way this past year). I actually found that the boat had less tendency to stuffing the bows when the spin was used.

The "stock" set up for the 18 used an 11.5 foot pole, the max people told me that would be trouble-free was 13.5, maybe 14. I set mine up so I could experiment, starting with 12.5 with the capability of moving fittings to get 13.5 if I wanted. I wanted longer length to move the spin forward and reduce the chance of closing off/backwinding the rest of the sail plan, but was worried about incurring lee helm. 12.5 seemed to work real well, no vices helm-wise. Unfortunately the boat got hit before trying out the 13.5 setup...