I have inmast so I do not have a sail in the way. There are no spare sheaves to be had since the outhaul sheave is always in use, even when the sail is furled and there are no reefing sheaves, but I could put a (very) substantial block on the eye that is on the mast to lead the line to one of the winches on the mast. I imagine that I would not have a spinnaker up in those conditions so those winches are available.
Heading back to Lake Ontario for this summer. Now in Bermuda and heading to Long Island Sound in the first week in May. Then on to the Hudson and the Erie Canal.