Gosh, photography sure has gotten expensive!
wrt your original question (I think...) If using a 210mm (or 8-inch) non-telephoto lens, think of the focal length as an f/stop, i.e., f/8. As your lens-to-subject distance decreases (camera gets closer to the subject) you will have to move the lens away from the film plane in order to hold focus. When you're close enough to the subject that the lens is 11 inches from the film plane, your bellows factor is 1 stop (f/11 - f/8 = 1 stop). That's the conventional rule of thumb, anyway. And it is completely independent of the state of dress of the model. I admit it's simplistic, but it dispenses with non-linearities and is easy to remember.
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