Hi CLB2.
Welcome to our Mattress Forum! 
You can see some of my thoughts about Northwest Bedding in post #10 here and a forum search on Northwest Bedding will bring up more information and feedback about them as well. They do make RV custom mattresses but I did not get in touch with them for quite a few years now to find out more about their other offerings.
They would generally be a better quality/value choice than most mainstream mattresses or major brands, and they are also open about the specifics of the mattresses. Outside of testing a mattress for PPP (Posture and alignment, Pressure relief, and Personal preferences) using the testing guidelines in the mattress shopping tutorial here (which is the most important part of a mattress purchase) I would make sure that you know the specifics of any mattress you are seriously considering (see this article ) so that you can make meaningful comparisons with other similar mattresses and keep in mind that a mattress is only as good as its construction and the quality of the materials inside it regardless of the manufacturer.
If you end up visiting them Iād be interested to find out about your experience with them.
Phoenix