Jim,

You are exactly right about my concern. I tension my rig with the jib halyard so both shrouds are tight. While I am sailing the lee shroud usually shows some slack due to mast bend and all the force on the windward side. When out on the wire, if the wind lets up, I see the windward shroud go a little slack (and usually go in right away). If you purposely leave slack in the shrouds with the jib halyard, as you say, a wave or bouncing around could let the mast come out of the socket as you come about and all tension is off.

Howard