Hi Scott,

If you're willing to dig into it, I recommend making a custom reader. I think it will end up being a lot cleaner. You can pattern after the one used in LABKEY.ext4.Store, which is basically doing the same thing you need. You can also consider convert() on Ext.data.Field, which is also designed to do the sort of thing you describe:

http://docs.sencha.com/ext-js/4-1/#!/api/Ext.data.Field-cfg-convert

If you end up overriding the reader, I would suggest adding 'requiredVersion: 9.1' to extraParams, in order to return the results as ExtendedSelectRowsResults. This means it will include both a displayValue and value for each field. If you need to display these data, that might end up being important (lookups, for example).