Sorry for late reply, i didn't comme here for a while.
I'm sorry if our contrib disable the pptp VPN, but a bit surprised, we don't deal with anything that is relative to that.
We make a large use of VoIP over VPN but, since we get a lot of problem with the windows VPN (PPTP), we have decide to use an other VPN, called OpenVPN, based on SSL.
We made some minor modification to the Swerts Knudsen howto for OpenVPN to be able to use it in "Bridge mode". This VPN is rock solid and is ok to transfer all protocols (neeeded by Asterisk).
You will find our contrib here :
sme.firewall-services.com/files/how-to_OpenVPN_SME_7.pdf
There is a minor bug in this version when dealing with an other local network than the SME's local IP range (i.e. : if you add a local network an a gateway to join it), we have fixed it on our production servers but not yet updated the how-to.
Let us know ...
A+,
RV.