Just to state what might be obvious: bracket...
As this is a probably non-repeatable event (I'm guessing the "perfect alignment" that will make time end, or whatever) that would mean several cameras. Beg, borrow, but don't steal, every Speed Graphic you can find, make a rack out of lumber, and line them up. Several films, several apertures, several lenses. Obviously, keep working on the testing and don't leave us in the dark!