The mount arrived tonight (thanks, Steve!) in a plastic bag including a brief sheet of instructions and two (SHORT) screws.
The mount is very much to spec for the Doctersight's 4 lug recesses and two screw holes. In fact to get it all lined up I had to start the screws first (more later), set the rear lugs then 'snap' the front lugs into position when everything was tightened down a bit to get it all lined up perfectly.
The BIG problem was that the mounting screws that Daniel Defense provides are TOO SHORT. They were were not long enough to allow starting the screws before lining up the lugs. What I found was that if the lugs were lined up first it was just enough to bring the screw holes out of alignment and the threads wouldn't engage.
Argh!
Luckily I have a Doctersight AR-15 mount with slightly longer mounting screws on hand. Using these screws I could get the threads engaged before dealing with the lugs. This brought the sight into alignment with the base and in turn allowed a perfect fit. The longer screws allow a more secure mounting but did not interfere with the close tollerances of the DD mount/ACOG fit.
Once the sight was set it was time to place the mount on the ACOG TA-01NSN. The rear sight was on tight enough to require a t-handled hex wrench but I was pleased to see some substantial screws holding them in place. The swap was easy and everything fit together like a Swiss watch.
The only thing left to do now is get that bloody luminous front sight post off the NSN without using dynamite!
Oh, and get used to the 'chin weld' needed to use the Docter!