[Freeswitch-users] Modifying fax headers

Hi, I have the same problem/questions Peter Steinbach had in this thread from 2014: http://lists.freeswitch.org/pipermail/freeswitch-users/2014-May/105196.html Is it in the newest releases of freeswitch possible to make this changes without modifying the source code? If it's not, can someone tell me which files I would have to change? Thanks, René