[phenixbb] Best practices for modified aminoacids

What are the current best practices for modified aminoacids? I have a peptide with and N-terminal Acetyl-proline which I am trying to model. The initial approach was to locate the aminoacid in the chemical components dictionary (N7P) and replace the residue in coot. Unfortunately the link to the next residue is not recognized, so the residue is just floating about. Next I just added an acetyl next to the proline and added some restraints in the .def file. That sort of works, but looks a bit cludgy. Is there a way to do this more cleanly? Cheers, Carsten