I think you should move the new XSLTs to the xslt folder (https://github.com/geonetwork/core-geonetwork/tree/develop/web/src/main/webapp/xslt) as proposed when the admin was rewritten (https://github.com/geonetwork/core-geonetwork/wiki/Refactoring-Admin-console#service-configuration-in-web-inf). It will be easier to deprecate old UI at some point if we do that.