The gradients from the original 150x100mm system is just too wide to be useful for these cameras. The Seven5 is much more narrow.
Not being much of a math person (which is actually a gross understatement), it would seem to me that the diameter of f/8 (etc.) on a lens of a given focal length, on a given sensor size (E.g. APS-C) would be identical regardless of the form factor of the lens or camera body. Ergo, the "blend area" neither no narrower or wider than any other camera w/ the same parameters.
Or, does the diameter of lens elements themselves have some sort of influence on the relative "actual size" size of any given aperture? And if this is the case, grad filters would then seem to have "relative" wide-narrow parameters for all lenses depending on each len's physical dimensions.
Somebody fill me in where I have it wrapped around the axle.