When I replaced my engine (CO200) I considered many different options for shoe horning the engine into the same spot as the Farryman. All of these required changing the rear mounts in some way. The engine dealer convinced my that I should mount the new engine with the mounts as designed. They told me that changing the mounts could interfere with the vibration damping, which is probably true. It seemed I would need a custom exhaust elbow also. So I chose to move the engine forward a few (four???) inches. I don't regret this, as it opened up more space around the engine.
I had an experience that convinced me that Contessa 26's need seacocks on the cockpit drains. My boat had engine problems one day, so I opened the engine hatch and three or four beefy freinds piled aboard to 'help'. Combined weight in the cockpit was well over seven hundred pounds. After a moment I noticed that water was backing through the cockpit drains and over the after edge of the engine hatch, into the bilge. In otherwords, we were slowly sinking. To stop the sinking I sent two helpers back to their boat.
It occured to me that if the boat took on enough water from a leak, and if the engine hatch was open or the hatch gasket leaked, the leaking would only accelerate once water started going over the edge of the hatch. Think of it as the boat having an effective freeboard of about two inches. Cockpit drain plugs would solve this, but would not take care of hose problems. So the next winter I put in two seacocks. I exercise them a few times per season.
[soapbox warning=on]I suspect that these cockpit valves were left out of the CO26 as a cost saving measure, perhaps with the rationalization that they would just sieze up anyway. The fact that other sailors let their cockpit valves sieze up is irrelevant to me, as it should be to designers and builders. Designers and builders should not compromise their practices based on the poor maintenance habits of the typical sailor, particulary in the case of a supposed 'blue water' boat.[soapbox warning=off]