I have used plugs rigged as shown in the image that I posted, since the early 80's. The majority of fish that I hook are hooked in the back half of the upper or lower jaw, occasionally I hook them in roof of the mouth, or in the tongue. I have never hooked one deep enough inside the mouth to even come close to the gills, probably because of the large size of the plug/hook combo.
I have inflicted far more fatal wounds to fish with herring than with plugs, even though I use plugs more.
You will also find that if you are fishing in an area where shakers are abundant changing to a 4" or larger plug will drastically reduce the damage you do to the population of shakers while still allowing you to catch keeper size salmon.