we just bought the 3670rl on Friday and are planning to do the same thing, cut down the fiberboard base and put a queen size mattress back on it. I had tears of frustration trying to make the king size bed by myself. We had just bought a deluxe mattress for our older Coachmen that I had gotten quite accustomed to. Not to mention, I bought a cheap set of 300 tc king size sheets which don't quite compare to the sets of 800 tc queen size I already have. On top of that, I needed a GPS to find my Husband,,, lol,,, Oldlthrnecks girl
Oh, and i have a question,,, what did you use to cut down the board? I would hate to damage the base.