The customer and I agreed upon 4 oz fiberglass when he looked at pros and cons of lighter methods and structure. He also just might put them in the water for children, even though they are not really designed for any particular person or weight and will be moved about some. He also wanted them to be real kayaks and built the same way as a larger boat. But we will save some time in that they will not have any hatches, but two bulkheads inside anyways. This means I do not have to clean the insides as much (back aching work anyways and not my favorite part).