I'm eager to try out my "new" helm seat, which is a re-purposed mini-van seat. I've sat in in for a few minutes with the boat on the trailer, but of course that's nothing like spending a day underway. Being a car seat, it slides forward and aft, plus the back angle is adjustable via lever. I'll likely post up after using it for awhile to say how it worked out. Who knows, it may be a total failure (although it won't be hard to improve on stock).
It is slightly heavy, and does have some steel parts, being as it's from a car. But I won't be taking the C-Dory to Tahiti, so it may be fine.