Ah... one, in both PHRF and under the one design rules, you aren't supposed to change your rigging tension after the prep signal.
Two, your tension isn't changing, the rig's loading up. On any conventional stayed rig, when you go upwind, the rig loads up on the windward side, and unloads on the leeward side. That's fully expected. On most boats, properly tuned, the lee lowers go sloack when your properly powerd up and heeled over, and the uppers get softer as well. A fair bit of the load generated by the sails is lateral. (Hey, that's why boats heel, pretty much) All that load's pulling against the windward shrouds and towards the leeward ones.
- David
