Bill,
I am always trying to learn and still consider myself a student but after studying these things quite a bit for a few years, the following is what I have found to be common.
If you intend to make an American piece from the north, the Grinslade book is the best out there.
If you are making an English gun, I would not use any carving on the fore end at all unless you are doing a late 17th to very early 18th century piece. Even at that, all did not have it in that frame and pistols seemed to carry the trait more than fowling pieces. The English carving on fore stock areas I have seen does not look like any of the "British Style" pieces in Grinslade's.
If an English piece of 1735 manufacture forward is intended, no carving should be used to best represent the period.
The dog knot was more predominant in the early part of the 18th century but co-existed with those that did not have that feature.
I have a few pictures of early 18th guns with carving on the fore stocks on my computer. I can send them to you if you shoot me an email. Most are of the side profile though.
James