I just dont simply see the benefit using 2 routers. If you must, try this:
Modem -> Router 1 -> Router 2 -> VP-100
1. DSL Modem: I assume this modem would give you 192.168.x.x address if I understand this would be NATed firewalled
2. Router 1: assign LAN IP as 192.168.10.1 / 255.255.255.0
Plug the modem to WAN (it would automatic obtain public IP or private IP, depending on modem setting)
Enable DHCP if you plan to plug computers to router #1
3. Router 2: assign LAN IP as 192.168.20.1 / 255.255.255.0
WAN Static IP assignment: 192.168.10.2 / 255.255.255.0 with Gateway of 192.168.10.1
Plug the router #1 Port 1 into Router #2's WAN
Enable DHCP if you plan to plug computers to router #2
4. Plug VP to Router #2 port #1. Assign VP IP as 192.168.20.25 / 255.255.255.0
Gateway of 192.158.20.1
DNS 1: 208.67.220.220
DNS 2: 208.67.222.222 (These DNS are OpenDNS.Org and more reaible than ISP DNS)
Try using public IP of auto-detect first.. if fails, try using 192.168.20.1, if failed, try 192.168.20.25.
5. if modem is firewalled, set DMZ to whatever modem assigned to Router #1
6. assign DMZ to whatever it assigned to router #2.
7. assign DMZ to VP 192.168.20.25
this *should* in theory open path from modem to VP totally opened via DMZ. Plus you have two LAN zones.
Good luck!