[HECnet] HecNET via 3G Dongle

Guys, Looking to tap into your collective knowledge. I'd like to set up a 3G dongle for the DEC Legacy event. The plan will be to add my machine as an area router then other participants machines into that area. Steve Davidson has pointed out that there are decnet numbers allocated for experimental purposes. I think I understand how to setup my 3G dongle to connect to the internet via an ubuntu machine. I am happy setting up a DHCP and DNS server on the same machine. The bit I don't understand is how I would fit the hecnet bridge into this network. Normally on my DSL router I have a port redirection rule setup on port 4711 to point to a Debian based box on my LAN. How would I achieve the same effect on a linux box? If I run the bridge on the same box, does this negate the need for a rule? If all this works, is there a restriction of one decnet area per lan segment? Can I run two areas on my side of the bridge? Thanks for the help, Mark