I am afraid your summary is as poor as your understanding.
You said - "but as D200 brackets do not fit the D300,"
I said - "The Kirk D200 "L" Bracket DOES fit the D300, I have one fitted!"
You have not tried a BL-D200 on a D300 - "I have to admit I have not tried a Kirk BL-D200 on a D300+ I HAVE and do daily!
"but I will post a link to this thread over in our Tripods & Heads Forum, where our resident experts reside. Hopefully someone will come over and shed some light"!!!
There is NO light to be shed - Mr Tilley, listen, take a deep breath, it fits. My D300 is sitting here next to me. It is "wearing" a BL-D200. It has just been removed from my Gitzo Tripod that in turn has a B1 Mono ball Head.
"Resident experts" - what breath taking arrogance! How much more "expert" do you need to be? It Fits, I use it! Any "experts" wish to argue?
I have not taken this personally, but your last post reflects an arrogance and stupidity that is almost beyond belief and the like I have not witnessed (outside of Politics) for some time!
Within the big scheme of things it probably matters little!
Congratulations, I am rarely #### off, but you have succeeded!