This is a cut-a-way photo i made of a section of deck that I first potted with epoxy then countersunk. I then wrapped butyl tape around the bolt head, tightened it down and left it there for a while. I then loosened the bolt and began pushing up from the bottom. There is no movement on a boat, with a mechanically fastened deck fitting, that will even come close to that amount of flex and stress on a sealant.
Remember this stuff has very low adhesive properties, unlike 5200, 4200 or any other caulk tube type sealant, and cleans up quite easily with paint thinner. Adhesion is not necessarily needed flexibility is! This stuff will out stretch and out flex any caulk tube sealant you can buy in a marine store..
Of course you must always bevel or countersink the deck side so you can fit more sealant in the gap. The more sealant the more allowable flex. If you look close you can see the beveled edge.
Yes I finally got sick of trying to describe the process of potting holes and countersinking so I took some pictures.