Hi Jacob,
Actually, I think I found how to override the iso/aniso decision: under "global parameters," set aniso cutoff to lower resolution. Seems to be working.
Ok, let me know if it still does not do what you want. Also you can always do: Refinement settings -> Modify selections for: choose "Individual B-factors" and you will get a pop up menu, where you can tell what atoms need to be isotropic and what atoms need be anisotropic. For example you can type: Isotropic atoms: water Anisotropic atoms: not water
Any thoughts on the more general question about aniso refinement in the case of truncated data, or +/- twinning?
Try both and see which one works best.
Seems twinning changes ML refinement to LSQ, but I am not sure how that changes this.
phenix.refine uses LS in case of twining. Pavel