After many many hours of research, it appears the RV042(g) is not capable of this process. However, i did find a nice work around. I have spare RV's. On the network that has the public open IP address, i have a RV042 as the primary. The inside router to forward back MUST be an RV042G or a RV042v3.
I setup the primary router to port forward ports 600000-60020 to the internal RV042v3 router. The only port used on the Internal router is the WAN port. It is setup to port forward ports 60000-60020 to the IP address of the off-site VPN Private IP address.
Public -> Primary Router -> Internal Router -> Primary Router -> VPN -> Remote Site Network
The primary router would not forward a packet from WAN to VPN, but it will forward LAN to VPN. So, by me putting an internal router, the primary router then sees the traffic coming from the LAN and then has no problem forwarding the traffic.
The IMPORTANT key to this is that you must add as a SECONDARY (Not primary) IP/Subnet to the internal router matching your Offsite Subnet. You then add an additional ROUTE to send that subnet back out the WAN. Without this, it will not port forward the packets back out the WAN connection where it needs to go.
Also, the second thing to remember, is being you do not have any lan ports connected to the internal router, you need to allow remote administration on some random port, and that port MUST be port forwarded on the primary router, otherwise you will not be able to administrate the Internal router.
I am happy to report that we can now receive SIP initiated phone calls to our offsite network even though they are completely nat'd and can not DIRECTLY receive incoming connections.
