Mark
What exactly are you expecting to happen with this statement. Just so we agree, this statement should translate any packets with a source address of 168.117.100.20 coming from the outside of your firewall to 10.97.0.1 as the packet is passed on to dmz2.
Is this what you expect and when you say you are still seeing 10.97.0.1 on the outside interface do you mean the return traffic going back out from dmz2 to the outside ?
Jon