2.54 cm to an inch. Try remeasuring using inches.
It might be easier measuring the diameter rather than the circumference. If you don't have any calipers, use some open ended wrenches. If you don't have any available, take the mics to a Sears or someplace that sells tools and use one of their display models. Or you could just put the mic against a large book and place the measure across the top of the mic body and see how wide it is. A quick rule of thumb is 19mm = 3/4 inch.
Taking your measurements, your mics are ~2 1/2 inches around by 4 1/2 inches long? Just measured a Nak body, it's 66mm circumference and 21mm diameter. The AT8410 will handle the diameter with no problems and the metal cage is 3 7/8 inches so by the time you add cables, you should have no problems, especially if you use a Shure vert bar. Between the vert bar and the mounts there are an almost infinite number of adjustments. If you can't get enough spread, just keep a t-bar or two, standard and long lengths, in your gear and you'll be able to use almost any configuration imaginable.