The guide that was written regarding belt mount regulators and the ability to tuck the hose in your garment fails to mention 2 things.  Doing that goes against every OSHA/NFPA requirement and gives a false sense of security, you can never filter out the CO gasses.  The other important thing to consider is that MSA has discontinued manufacturing the belt mount respirator and will not longer even supply parts in a few years.  I can't imagine anyone purchasing an SCBA with a belt mount respirator.