Hi Picard:
I also have the same sheeting system on my 1974, and have experienced the same problems that John has. The mainsheet block and cam cleat on my boat are mounted on a square wooden pedestal on the port side that raises them off the deck by about 3", just enough for the bitter end of the mainsheet to clear the cockpit coaming. This is just my first season with Ephesus, and I don't know whether the pedestal was installed by a former owner or by J.J. Taylor. I suspect the former. However, I didn't experience much problem releasing the mainsheet when required, except that it required quite a jerk of the arm. There's another Contessa at my marina with the same mainsheet set-up. He doesn't have a pedestal on his boat. Instead, he has the mainsheet cam and block on a hefty lanyard that appears to be about 6 - 8 " long attached to a sutstantial eye on deck behind the port corner of the cockpit. This 'floats' it above the cockpit coaming and probably makes it easier for him to cleat and uncleat his mainsheet.
Prior to sailing season this year, I decided to replace the original mainsheet blocks at deck level on the starboard and port sides with larger Garhauer blocks on a swivel. Bad idea. The swivel on the starboard side tends to eventually twist while I'm sailing so that the mainsheet also ends up twisted on that side. It didn't do the same on the port side because it led from that block to the block and cam. I'm going to replace the new block on the starboard side with the same block I took off which still works well. I'll do the same on the port side since the swivel wasn't really necessary on that side anyway, and so that both blocks will be the same. That was a costly experiment.
As with John, I also find that the mainsheet rubs on the gate latches for my lifelines where where they connect to the stern rail. I turned each latch around so that they open on the outside, so at least the mainsheet doesn't get caught in the latch and chafe as badly. Still, a bit of clear hose over the latch that can be slid off and along the lifeline when it's time to open the gates might fix the problem altogether. I just haven't got around to it yet.
I know some owners have installed travellers on their boats, and I wondered if that might offer any advantages over the original system that we have. I had a traveller on the Bluenose that I owned prior to Ephesus so my current mainsheet setup was new to me as well. As far as I can tell, the port and starboard blocks give the same advantage as moving a traveller car to leeward to increase sail twist. However, I can't honestly say that being able to move the traveller to windward in lighter air or to power up through waves or chop would have made my boat sail faster. Someone with a better grasp of physics or with more sailing experience than I might be better able to comment.
Cheers.
Carolyn