Matthew and Peter,
re my problem with tabernacle screws pulling out, I suspect that it not due to mast raising/lowering, I doubt that the forces are sufficient in normal circumstances. I have noted that mine are lifting from the rear which suggests fore/aft movement, perhaps with a lateral component. I note Peter's comment re shroud tension and usually (except in light weather) tension the rig with the jib system (have recently changed to dyneema on the jib halyard) but note that there is still considerable slack in the leeward shroud. Even with sweating the jib halyard the rig cannot be tweaked to the extent that it is rigid, in any case the jib shape suffers at high rig tensions. I have concluded that in order to get sufficient rig tension and allow some latitude for playing with sail shape that a short bowsprit and dedicated forestay is in order.
Now I understand from Graham Wickenden that Matt Newland may enter with his comments and I will be very interested to hear those.
In any event it seems that this is a topic of great interest and I will be keen to read further discussions.