3.3/3.4 actually changed to rp_register_directory_map. What I'm not sure about is that there are already two packages that do this, and I can't find where the calls to rp_register_directory_map are. acs-core/request-processor-init.tcl is where all the packages are registered, and seems like the logical place to do other custom directory mapping, but that's not where the existing calls are.