Mac Printer driver substitution in XenApp 7.6

I am having an issue with driver substitution on the Mac clients.  On our 4.5 farm the amc printers would remap with substituted drivers if i used the Printer name (as opposed to the driver name like windows clients).  However, in the 7.6 farm I cannot get the drivers to substitute regardless of whether I use the printer name, or the driver name (at least I assume it is ) for the mac clients.  The policy is Applying as i have tested it successfully on a PC based client.  Am I missing something fundamental, or is there another method for mac driver substitution.  THe only thing I can think of is that I am not getting the correct driver name as it is reported by the client, but am unsure of where that name is defined on the Mac.   SInce I have first tried to look at this issue and based off other issues with Mac I am beginning to think that this is not possible.  If I recall I can set the default driver to be used as something different than the HP Color LaserJet that is standard, but in that case I think it is an All or Nothing.  I do not know of a way to selectively set substitute drivers by policy like I do for the windows Machines.