Instead of doing the custom metadata url, there is an option to modify the osp config to get around OSP using the wrong end point url. Follow the guide for OSP localization at www.netiq.com/.../.
The file you will need to modify is WEB-INF/conf/current/idm/services/authcfg.xml. Find ssoRedirect="true" which will be in the following block near the bottom:
And change it to
After making the change follow the instructions for repackaging and using the jar.