I see.  I understand the desire to conserve flux, but I hadn't twigged that the convention being adopted for this specific class is that the `ShearWCS` is a transformation that also preserves *area*.  If I'd been more attentive, I would have seen that from the factors of `sqrt(1-g1**2-g2**2)` in the denominator in the definition given in the docstring.

Would you object to me adding `Area is conserved.` to the second line of text in the docstring?