Timbo,

if your leech is flapping there are several other things to try before you shorten your spi pole. First thing is to assess the state of the spi and perhaps tighten the leech line a bit. A small hook to windward in the leech is better than a flapping leech. If that dont help, you think the spi is not worn out and your mast rake is OK, I would have looked at spi block positioning.

Sorry for going off topic.