[phenixbb] Assigned occupancy refinement

Hello PhenixBB, We are interested in refining 3 distinct backbone conformations of a loop (A, B, C). Our crystals are very high resolution and the density is fairly distinct for each of these conformations. In the simplest case - each individual backbone conformation has one residue in two alternative side chain conformations. (A1,A2; B1,B2; C1,C2). We'd like to keep each pair of conformations assigned to the respective loop and then refine all six occupancies. Is there such an option similar to the free parameters in shelx also available in phenix? Thanks, Marcus