[Freeswitch-users] how to pass arbitrary headers from A leg to B leg when bridging

Is there a way to pass any desired SIP header that I receive on an A leg through to the B leg? I have looked at sofia_glue.c, and I see either special cases for certain headers being handled (e.g., Alert-Info), or support for only X- or P- custom headers. I have a specific need to pass the Proxy-Authorization header that I receive on an A leg and have that same header and value contained on the B leg INVITE I generate (I have authentication turned off for this configuration, because I don't want FS generating challenges, I just want it to pass through the relevant headers). Is this possible without hacking the code? Dave