Why are you redirecting to the delimitedTextReportRenderer.form here?  Two problems with that:
a) That page doesn't exist in this branch, so I get an error when I try to submit the form
b) This isn't where this should be defined.  A better solution would be to follow the existing pattern we have established for create/edit url mappings by type, which we have used for editing cohort definitions, dataset definitions, etc.  Look in the web.controller.mapping package for these MappingHandlers, and then search the code for examples of how we have used them.