[modeller_usage] Modeller Model Building Inquiry using existing PDB cooridnates

Hi I want to build a C and N tail and one cytoplasmic loop that are missing from the PDB Cryo-EM 3-D coordinate file of a transmembrane protein. These regions were too dynamic during their Cryo-EM process and therefore are left out of the structural file that the investigators input into the PDB. Is there a way to model just these missing tails and one loop WITH the rest of the protein meaning not modeling the regions separately and then stitching them into the existing PDB coordinate file subsequently? I did not see this methodology amongst the Modeller tutorials but think it is best to maintain the fidelity of the protein as a whole i.e. non-stitching.

Thanks:) Joel