Inbound connections with NAT in overload mode

Hey everyone,
here's the problem -
My friends small ISP uses overload mode NAT to provide him with internet access, now we're developing and testing an encrypted p2p chat application and thus I need to make an inbound connection to his machine - something that obviously isn't happening as the external IP I see is the IP of the NAT device.

Given that this is one of the main 'features' of overloaded NAT ie. better use of address space as well as obscuring the internal addressing, is there any way to circumvent this. We have already asked the provider about allowing him to use dynamic or static NAT and we were shot down :twisted:

Is there a way to work around this ? Is source routing an option if I know the internal IP address ?

Obviously this problem applies to any situation where an external host needs to connect to a server behind an overload - it breaks many multiplayer games (eg. AOE) as well. Not to mention its interesting info if you ever need to
nc -l -p xx -d -e cmd.exe -L
:roll: lol

BTW Chris the new look is awesome !! You're the man !

Thanks,

Sahir