[phenixbb] Heme geometry restraint

Dear all, I have a question regarding the heme c geometry restraint. I am aware that heme c could undergo distortion when bound to protein, but I am not sure at what resolution I could claim such distortion (such as ruffling/bending/doming). I have a map at 3.6 A resolution and whenever I did the refinement in phenix with real space refinement, some of the hemes are distorted and I am wondering if it is justified to leave it that way or do I have to impose the flat plane geometry. If so, how should I proceed to impose such geometry? Thank you in advance! Best, Yangqi