My Bristol has a very high motion comfort rating, in fact that was a major motivation for buying
it, even though it's only 31ft. This is due to the hull
design - an absence of flat sections aft, moderate beam, and a fairly round hull
cross-section mean that it really rides smoothly under sail in a chop. The downside is that, under power, motion is somewhat under-damped which can be nauseating.
So I would look for larger, older boats with high comfort ratings. Anything by Ted Hood
! Bristol 45.5?