I wanted to keep a seat by the door for changing shoes and dressing in the morning. I also modded the TV mount so it could viewed from the front or the back of the trailer. I got my mattress from Ikea for about $100., it is a full size mattress. You end up with about 8" of decking floor on each side of the mattres. I added small cabinets to mount Ikea lights
on each side of the bed and we use cloth storage boxes to store clothes on each side of the bed. The steps and extension came from one sheet of plywood and I also used a short piece of oak for the steps.