ok right there is my 2 new boxes for this winter. 1 foot by 1 foot and they are each 8 feet long. cover in 1/4 HDPE on the pink and black one has glow in the dark paint around the edges
countersinking is making a shallow divit for the head of the screw to sit below the surface of the box. you can buy countersinking bits. or drill your on holes with a drill bit the same size of the head of the screw
we had two like 4 or 5 hour sessions on it it and it worked great. the only problem is if you come off the side the edge scrapes alittle but i knew that would happen and it doesnt happen to often.