Jon,
Thanks for that, I did realise afterwards that the answer was probably in the book. I will certainly join as soon as the purchase is confirmed.
The luff lengths are what i was after. I think that the mast must be taller than i realised, a second-hand Dragon spinnaker is going to be a little on the short side with a 7m luff length. At least it will help us home from a picnic better than nothing, we are some way from racing or wanting to buy brand new sails for her.
If you see a Seal on the Orwell, in Suffolk, next summer with a spinnaker flying rather high that is probably us!
Antony