VPN bridging issues - DDWRT

I have a hosted Freepbx server on a VPS with a public IP.
I have enabled the vpn option and set up a user with vpn access granted.
On my home network i have 2 Polycom VX410 phones.

I am connecting my DDWRT wrt3200acm router to the vpn - which it does successfully. I have tried every combination of TAP/TUN, Bridged/un-bridged and Subnets but i cannot get the networks to bridge.

When i use tunnellblick on my mac to connect i can access the local interface of the freepbx server and my softphone connects successfully and sends and receives calls. But as soon as i try to use the bridge setup on my DDWRT there is no connection.

I would like to be able to access the freepbx server as a local IP to avoid any issues and make the use of ip phones on the home network easy.

I have trawled the internet for the whole day now and I’m stumped.

Does anyone have a good resource or guide on getting this working?