There are two companies in NW Montana that make custom fishing frames, both very similar, so maybe they're the same company??? Anyways Custom Street Stuff and Montana Raft Frames. They have some pretty innovative ideas and use mixtures of NRS and speed-rail (like DRE) fittings, plus welded risers, foot bars and rod holders and anchor systems.
I agree with Sembob, I've had a NRS frames for a dozen plus years and there is nothing loosy goosy about them. I've never had things loosen up but if it did happen it's nothing a 1/2" ratchet can't take care of.
I built a fishing frame last winter that I really like. As it turns out it's all NRS fittings (low-pros) because I already had them, but if I were to be buying all the components I would have used both speed-rail and low-pros, each in specific places. I had a few of the parts custom bent and still have some tweeks to do this winter but too me it's nearly perfect.
If you're not a DIY'er working with one of the local(ish) frame companies might get you a combo that's exactly what you want, with some degree of modularity ('cause nothing is perfect for every situation).
"If you dont do it this year, you will be one year older when you do"