Alan,
I also hope that you and your family had a wonderful Christmas. Some months ago there was an article in Trials Comp that showed how to set the sag on the Shercos. I believe that Bill Ibsen developed it. I have a copy of it and would be happy to send it to you. The dim they use is 2 1/2 inches for the sag.
BTW the Polini manual is fantastic, if it is OK with you I will share it with the Sherco Dealers.
Wayne