Hi guys, I found my receipt from when I ordered new foam for my gaucho and twin bunks. I had the original couch that they used as a template, although it was pretty deteriorated.
Twin bunks: 33" wide x 74" long - they are just 6 inches skinnier than a standard twin size mattress, FYI. I went with a medium density foam that was 5" thick, they are comfy!
Seat: 21" wide x 86" long x 5" thick (if my memory serves me right this was a little bit too long and I had to trim it a few inches, so 86" may have been a typo, sorry!)
Backrest: 15" wide x 76" long x 5 " thick
Hidden piece: 12" wide x 76" long x 5" thick
Now, this obviously doesn't take into account the curves and angles for the backrest and the hidden piece since they rest up against the curved walls of the trailer, but the foam is really easy to trim using an electric knife to get it perfect. Just like carving a turkey.