Hello Jack, ....
I've used Guar Gum in a few BH recipes at 1 tsp per pound, sometimes tried a bit more, sometimes a bit less. It didn't improve binding to a great degree but it seemed to hold juices from disbursing. If you do use it, mix it together with all your other dry ingredients before adding to the wet ingredients. Doing so helps ensure it's evenly distributed in your mix.
This is anecdotal but I've stopped using Guar Gum as well as Agar Agar or Xanthan Gum because when doing wipe downs at WC intervals there seemed to be an increase of slime on tank walls. I've returned to using plain ol' gelatin.
Stan