Ernie......I don't really know of any hard and fast rules concerning underlugs. On a half stock gun you could live with one
or two, whatever suits your fancy. On a 38" barrel I would use three, on a 42" barrel, probably four, but you could also
use just three. Anything over 42" I would use four. As for placement with three or four, I usually place the rear one at
about 7" from the breech, the front one about 3" to 3 1/2" from the muzzle, and the others evenly spaced between them..........................Don