To give strength to the v-berth area without adding weight, I have built three I-beams. These things are so cool. I used 5mm luan for the webbing and then used 1/4" ply for the caps. I glued these, and then laminated the web on both sides with 6 oz cloth. They turned out super strong, and weigh less than a pound each. Now I should be able to use 1/4 inch ply for the v-berth "floor"