I guess I misunderstood the question. If it was, "How strong does it need to be?", then destruction test it with two fourteen year-olds strung out on glazed doughnuts. It's only a few feet drop to the
water, and any damage that might have ensued could have happened
offshore in a gale, anyway. If it was, "How weak can I make it and still survive?", get the fattest friend you've got, who won't sue you for trauma, and have him make a foot-first leap off the pulpit onto the tramp, with a bounce over the side. Hold up the score cards for form and check to see if anything broke on the
boat. I tend to err on the side of the fourteen-yearolds, because tramps are irresistable playgrounds, for all types of play.