I sailed very few races aboard C=M 66'. I have seen 27 and reported 17 1/2 average on a course during S.O.R.C. Many people have sailed the boat, they can give their version.
In the Marblehead to Halifax race she crossed the finish line so early that there was no boat to fire the gun. The record was held for many, many years.
On the smaller Desperado 57'. Speed over 25 knots was so common that they had a tee shirt labelled, the "25 knots club". Speed, very seldom achieved at the time for a monohull. Especially for an I.O.R. designed boat.