Looking at the adjustable set ups for wishbones and stumbled across this on gartracs site.
http://www.gartrac.com/shop/451-580-...adjustable.jpg
It looks like a simple sleeve+ thread for the normal poly bush, I reckon in the true spirit of the locost/haynes builders this has a lot of benefits in terms cost , adjustability and durability. Does not look like it would be a problem to knock up .
Bob