I used to have the Griffin one on my vice but as time passed I just use the hook gap as a guide. After you tie a few hundred or a few thousand flies you instinctivly know what feathers to pluck. It's like a mechanic can look at a bolt head and tell you what size it is. With all the hook variations out there you can just stick with the 1x to 1 1/2x the hook gap.

Jeff