With my standing rigging down for reworking, I removed the 4 bolts joining the deck top mast step to the compression post in the cabin and then drilled down through the cabin top till I brought up aluminum from the compression post top flange below. Under the gelcoat and a layer of fiberglass is 1/2' of plywood. On my 21 year old boat this was perfectly sound. Beneath this plywood is solid fiberglass all the way down through to the compression post below. Thus for the H 33, only the top 1/2" of plywood has any significant potential for settlement or deterioration. I also drilled the box that the bottom of the compression post disappears into and found it solid fiberglass too. All in all, the H 33 has a robust and strong mast support structure which should be there for the life of the boat.