I ought to be able to select a residue and use my cursor keys to change its phi/psi angle by hand. Simply dragging the thing around with the mouse and hoping that it will guess what I'm trying to accomplish correctly seems inadequate. Since these quantities are well-specified, it shouldn't be a big deal to put their manipulation in user control, and it would make reshaping certain segments of the protein (e.g., removing twists or bends in a sheet, the problem I'm currently struggling with) much easier.