Here are some pics of what I came up with for a cheap alternative to those overly-expensive composting heads. I have been using this for several weeks now, and have been very pleased with the result. Works great, and is dirt cheap (no pun intended ). More details @ a thread I started on sailFar to describe it.
Tony - wow, that foam ply construct is just what I was thinking. I don't think I'll have time/money to implement it, but - great illustration, glad to know I'm not totally off base.
Ebb - I'll follow this post up with more of my external chainplate stuff; I don't want to hijack TonyG's thread (more than we did already... ).