Get a long tape measure. On a calm morning hoist each sail. Eyeball where each sheet will lead to on the deck
. The angle of the sheet at the clew of HHS sail can be hard to judge. And it changes the deck
position significantly. Borrow an experienced sailor to help guess, or go sailing. Deck sweeping headsails tend to have the sheet nearly vertical. High clew sails
about perpendicular to the luff. Room to move the lead aft is more necessary than forward.
With the sheet pulled tight on one side measure from the clew forward around whatever shrouds, rails and stays the lazy sheet will need to pass, then back to the lazy side winch
. Allow enough for a turn on the winch
, some for the knot
at the clew, some for a stopper knot
, and then a couple of feet more so that worn ends can be trimmed and still have enough length.