After a lot of experimentation, I finally settled on this rigging for the mainsheet. The sheet ends up at a Ronstan RF5 swivel 180. The device incorporates a camcleat and a turning block onto a hinged base.
One thought was moving the control from the end of the boom to the middle. This would put a lot of strain on the boom and clutter up the cockpit.
I decided on a rope traveller. Notice it is moved forward from the transom in order to give the mainsheet fewer things to tangle on.
You can also see the new thwart and winch in this shot. The boat came with a Davis Tiller Tamer which worked nicely- except lines got tangled in it. I turned the tiller over so the tamer is below the tiller. No more tangles!
A 3 part mainsheet seems to be about right. The automatic ratchet is probably overkill, but it works nicely.