ENH: refining replacement logic
ENH: refining replacement logic

mnicholl/MOSFiT,villrv/MOSFiT,guillochon/MOSFiT,mnicholl/MOSFiT,bmockler/MOSFiT,mnicholl/MOSFiT,guillochon/MOSFiT,guillochon/FriendlyFit,guillochon/MOSFiT,bmockler/MOSFiT,villrv/MOSFiT