Interesting rigging suggestions from Bill Shaw on this topic - recovered from internet archives of "The Pearson Current" in 1994 (I could not recover the drawing that was referenced):
QUESTION:
I am the owner of a Sublime Pearson 323 (#54). A question I have related to mast pumping. Since we have put on jib roller furling, I have noticed that at times, when no sail is set, the mast has a tendency to pump. I have played with rig tension in order to minimize the pumping.
ANSWER:
As for the mast pump, adding a roller furler will often do this. The big furled sail starts to oscillate and then the mast starts pumping. Try putting a line around the mast at the spreaders. Tie off the lower end way forward, near the stem head fitting with lots of tension. If this works, you can add a small block at the height I’ve drawn here, sort of like a boom topping lift. Sometimes, a line around the furled jib led aft will work.