In theory you could add track-risers and a High Beam Traveler Track that would span your companion way and give you somewhat better control of your boom (see http://www.harken.com/pdf/4524.pdf
). On your Willard, however, I question the benefit as the yacht is not one that could be driven to weather
very closely and would likely make rather too much leeway if brought up too hard on the wind
. You might find that adding a vang to control twist will allow your mainsheet to work somewhat better.
FWIW, you might find that two 2- or 3-part vangs, one on each side of the yacht, led through blocks attached to pad-eyes mounted just inboard of the bulwarks and then back to cam-cleats in the cockpit
is just what you need. With the vang taken up, the mainsheet will have somewhat less vertical loading which should improve you ability to adjust the position of the boom. In any case however, I question whether the yacht can reasonably do better than 35-40 deg apparent.