Hi,

Currently we have a series of SharePoint sites already created in which we have a custom field created as follows in a custom fldtypes.xml

Code:
<?xml version="1.0" encoding="utf-8" ?>
 <FieldTypes>
 <FieldType>
  <Field Name="TypeName">HierarchyTaggingField</Field>
  <Field Name="TypeDisplayName">Hierarchy Tagging Field</Field>
...