I think jonoashton is asking about the location of the hinge pivot point, not the construction of the hinge.
IMO, the best hinge for a JW is 3 sets of tension hinges followed by a full length compression hinge.
The compression hinge only gives too much.
Repost..."Tension hinge/Z hinge/over-under, whatever you want to call them, will really lock in the position of your elevon, up/down, fore/aft, and help to establish the perfect hinge line. A compression hinge alone is difficult to make accurately and doesn't lock it in.
Do a search for tension hinge and you will find some good pics and diagrams.
here are some links...
golden advice from Daemon...
and some pics...