Cisco Routers :: Using RV042 In Series With Another Router

I have been able to put two Linksys routers in series no problem but this doesn't seem to work with an RV042.I have a number of customers that need to connect to a private email network via a router based VPN, but since VPN traffic is not filtered in the firewall, I would like to use an older Linksys router to manage the VPN(s) and have it pass data in through the filters of an RV042 on the DMZ port.I am getting stuck on the very frist part of this. Although I can connect to both the RV042 and LinkSys directly (by adjusting my subnet), I cannot ping the Linksys when it is connected through the DMZ port even if I disable the RV042 Internet port.
 
I know both the Internet and DMZ ports work on the RV042. I suspected that perhaps the RV won't pass through private IPs and tried known available pubic IPs instead of the 192.168.2.x subnet, but still no ping.What would be limiting the RV in this case? Is is possible to setup the RV to work in series with another router? Is there any other way to filter VPN traffic?