Not sure if anyone is interested but just in case...
Here's what I did to the rig to try and improve things a bit. There was no room for a conventional boom vang to keep the boom level, so I went for a windsurfer-style wishbone arrangement. All bashed together out of whatever I had to hand, so it's a bit rough and ready, but if it works OK I can tart it up a bit later.
Here's a general view of the result -
The piece that slides on the mast and the piece at the end of the boom are small lumps of oak, and the 1/8" dowels are, I think, walnut from heaven knows where. Thin carbon rod would be more in keeping!
I held the tack of the sail down with the supplied rubber band and a small screw in the back of the mast.
(The messy glue around the mast is from an earlier attempt to fix the boom to the mast.)
The whole rig looks and feels much more like it should (or at least how I think it should) but I haven't actually tried it yet. I'll let you know how it performs when I have had a test run.
(Come on Martin, where's yours??)
Greg