Hi Solentfish
Although I keep GFD I am not entirely expert at correct showing etiquette for the breed ,I am in Norfolk and there are only a handful of breeders in this area , so when ever I go showing My "Greyfaces" they are always in a mixed breed class and I tend to go to the shows for enjoyment and am not to fussed about exact fleece length etc.
If you are solely in Greyface Dartmoor Class ,then it is a different matter and rules on GFD shearing dates must be followed.
If Hazelwood is reading this, I am sure she will help on this subject or if you read the news letters on the Dartmoor Society website their is a lot of advise on when to hand shear for showing.
Good luck at your show
Tilly