So for Plates 1-4, I think we know enough about how those were entered and made, in order to make some observations about them.
First, a 3-relief transfer roll, followed by a 6-relief transfer roll on plate 4. Actually, the very beginning of 1E may have been a 1-relief roll, but I digress.
After they got their bearings straight on Plate 1E (inverted transfers, top row right pane, etc), plates were entered vertically, left to right. Since things are inverted, that means 10R was the first entry and 91L the last. Because they were entered vertically, and subsequent vertical settings of the transfer roll, were essentially guide-reliefed by using the bottom of the last entry as a guide, that tended to make very even vertical rows (lets ignore 89R2, 99R2, - mistakes, etc).
My point is, as a result of the way they entered these First Contract Plates, the horizontal spacing and vertical alignment will tend to be pretty close on a row by row basis. That is why we can and do utilize this for those plates in order to plate stamps.
Moving forward to the later plates, Plate 11 and 12 are really a whole different ballgame. They were made many years after the First Contract plates, and just from a casual eyeballing of Plate 11 and 12, it is evident that the same process wasn't necessarily followed for them.
They are both 3 relief transfer rolls, but that is where the similarity ends, I think. Look at the Neinken map of Plate 12, for where the reliefs went. Its all over the place. There is some regularity, but overall, its kind of a mess. From what little I understand about Plate 11, it also has some real differences.
Where I'm going with this, is merely to gauge your expectations, and give you enough background information in order to fully process whatever data you get. I'm not sure I/(we?) know enough about plate 11 in order to fully make the statement that horizontal spacing and vertical alignment is going to work as well for this plate (or plate 12) as it did on the First Contract Plates. I will be very happy to be informed that everything is regular and "it all works", but lacking evidence, I would proceed skeptically.
I suspect what you are proposing may work reasonably on First Contract plates. Heck, it might work for plate 11 - I don't want to stop you, I just want you to understand that you are walking into the abyss with this plate. There aren't a lot of maps, and few flashlights to find your way around.

Good luck!