I just noticed http://www.openldap.org/its/index.cgi?findid=6574 - this looks like it fixes the issue I mentioned in http://www.openldap.org/its/index.cgi?findid=6540? Is that assertion correct?
I couldn't specifically look at your issue (apart from the simple fix to allow cn=config to work). ITS#6574 should have nothing to do with your issue, as it affects back-meta in a part that has no code commonality with back-ldap, and slapo-chain is built on top of back-ldap.
I'm sorry I went back through this thread and got somehow lost; what's the exact topic now? I infer (from followup #14) that there seems to be an issue about chaining because slapo-chain seems not to rebind as expected. Could you isolate the problem in a minimal setup (slapd.conf or the corresponding back-config's LDIF, a database and a simple operation that can be performed with ldapmodify/ldappasswd or so) to clearly reproduce the issue?