Truth in assisting: haven't tired the same myself, but this might help:
http://tldp.org/HOWTO/Apache-WebDAV-LDAP-HOWTO/
and a question: is there a setting (object/field in schema) in LDAP for WebDAV?
I'll bet many folks would be interested in your efforts and solutions so please, if you resolve, post back! ;)
'spirit of sharing', Ken