Doesn't 314.23(E) come into play here?

Well Bryan that's what I thought....please read all the other post's and give us your expert opinion.

What say you Nick?

I could be wrong but I thought xxx.12 rules of things that are not permitted uses trump the other general articles.

I've read the other posts and have had this very discussion on other forums in the past. In my opinion, sometimes the exact wording of sections creates unintended consequences that were not conceived of before the wording was finalized in the code.

In these cases, common sense and good judgment on the part of the AHJ must be made to determine what installations are suitable or not based on conflicting information provided by the code or other recognized standards.

I popped this up over on ECN and they asked how can you make RNC "wrench tight"? so 314 must only refer to IMC or RMC.
352.12(b),<shall not be used to support> also says "... or other equipment not described in 352.10(H)."
That would exclude anything BUT a conduit body.
I understand this brings up an interesting problem since there is no real way to support a "deck box" that is not in a deck. ... unless we want to call it a conduit body

Since is is not a FS, FD, "cast" or "sheet metal" that might not be to far a stretch. There is sufficient space for the splices.

Bryan I agree common sense says the J box is probably not going to be a probl;em only supported by the RNC. My original objection was to hanging the transformer up there, only supported by RNC. It was after really looking that the actual language became troublesome.