The Dymondwood laminations are (apparently) not very strong. Getting the stopper just right, not too tight and not too loose can be problematic. And the woods do change dimension with moisture, which is abundant in a duck blind or from using (blowing).
I don't use the O rings because of dimension considerations. The stopper is drilled with a 1/2" diameter hole. The outside dimension of the stopper plug is 3/4". That means the thickness of the wood is only 1/8", not much to play with by cutting grooves for O rings which are almost 1/8" in thickness. At best you get only paper thickness left, not sturdy enough to suit me.
How do you do it?