@phil.davis:
The DMZ OpenVPN Server end will need rules to allow traffic in from 172.242.242.0/24 - if the existing pass rules on OpenVPN are not wide enough already, then add one.
In the DMS OpenVPN Server Advanced box, you can just tell it routes, no need to "push" them from the other end. e.g.
route 172.242.242.0 255.255.255.0
This tells the server end that the OpenVPN link is the next hop for reaching 172.242.242.0/24
From your description, I think that is all that is needed - allow the packets into the DMZ pfSense from across the OpenVPN, then give the DMZ pfSense knowledge about how to route the responses back.
That did the trick!
thanks ;D