per Alloys comments above, I might actually be better served by a different manufacturer.
Duramag Pride themselves on being half as light as their steel competitors. Sounds like I might want some thing a bit heavier duty.
Duramag sells a lot of truck bodies, including heavy duty flatbeds, that they make with aluminum. Their products are holding up in a commercial market where many users don't exactly baby their beds/boxes/etc.
Although you could look for a custom fabricator who does all sorts of different products made with aluminum, and you might be fortunate enough to find someone that can actually fabricate excellent results for each and every project, chances are you will need to pay top dollar for his/her/their work, including the design time.
Or, you could find an aluminum fabrication company with a proven record that specializes in commercial aluminum truck-beds/boxes/etc. Research and development costs will be spread across the many units they sell, and their products will have been tested under real-world applications. Such a company might offer custom work too, and be able to tell you if the custom work will be simple or require a lot of design and changes from their standard units. Such a company might also to be able offer suggestions such as, "Well, it will take a lot of extra work to build it that way, but if this will work for you, we could just modify ...".
My understanding is that you need a support for a camper-box, which a flatbed could do. Your camper-box will be spread out over the flatbed, unlike many loads secured to a flatbed which often place the entire load on a small part of the flatbed. The mounts that
@IdaSHO designed and fabricated might be different than anything Duramag has built before, but they have likely added custom mounting points to a number of their truck-beds/bodies/etc.
Please keep in mind that you will likely be starting with an "incomplete vehicle" and that obtaining a flatbed from a company such as Duramag might make it easier to insure your vehicle than obtaining one from another aluminum fabrication company.
