I don't know C and C 27's that well as to when they started building the Mark V however I can tell you I have a lot of respect for the design in general. In the late 70's I sailed a C and C 27 from Barbados
to the Grenadines then up to Martinique
and back to Barbados
. During that trip we encountered 20ft + ocean swells in non storm conditions from a disturbance off Africa
Also encountered a squall off St. Lucia lasting a few hours that caused me to run bare poles.
Boat handled the conditions beautifully however with me being the only one aboard who knew how to sail there was a lot of vomiting and grumbling down below