I had originally designed the settees so that they would fit a standard futon width and the port settee would fit a standard length also. This would have saved considerable time and money by simply buying a futon and dropping it in place. The major disadvantage would be dealing with one very large "cushion" that would be difficult to gain access behind and below it.
We have been doing several large vessel interior refits at the shop lately and the crew has become proficient at wrapping panels and dealing with headliner, carpet, and foams, so I decided to go ahead and build the cushions in house rather than taking the easier futon route.
We bought some medium flex high density foam and set to templating the settee bunks.
We stacked 2x4's two high to simulate the thickness of the foam. This allowed for the angled seat-back and ensured the top of the foam would not be too narrow due to the angle.
We used the wood strips and hot glue gun method and made a template in the usual way then took it below and laid it on the foam and drew it out with a felt pen. An electric knife was purchased from the local Wal-mart kitchen center and was used to cut the foam.....it goes through the foam like a hot knife through butter!
The 13 degree seat back angle was cut "free style" by holding the knife at an angle and following the line we drew. It worked ok but I might make a jig for the angles on the rest of the cushions to get a more accurate cut.