[Ifeffit] Filter window shape for FT?

I've always been told that when doing Fourier filtering, the R-space window shouldn't have sharp corners. Artemis, for instance, allows you to vary this, and by default puts shoulders on the window. I have a user who now wants the sharp corners, claiming that it provides the best filtering. He describes this as "doing the FT in a region of R-space". What does the Assembled Multitude think of the risk of termination effects with a rectangular window? mam