PPTP and OPENVPN

Hi,

I'm using Openwrt on D-link DWR-921. I've successfully set 4G connection and everything else. After doing the research I was able to install PPTP client and route my LAN/Wifi on PPTP and 4G and anything else is working perfectly.
now I'm wondering if I can set up dual VPN connections on the router, one PPTP and one OPENVPN, and I installed OpenVPN client, configured well and it's connected, working.
Could anyone help me about how to set IPTables or firewall to do that? Plus anything I want is if both connections are dead modem routes the pure 4G on LAN/Wifi

Thanks