firewalling on "modem" link

Hi list,

Sorry if this has been asked before. I'm a reasonably novice m0n0wall user.

Yesterday I installed m0n0 as firewall on my ADSL line. I use a
SpeedTouch 780WL in PPPoA to PPTP mode (XS4All ISP, for those
interrested).
This was running before with some homebrew firewall.
Internet access on IPv4 and IPv6 are working well.

The problem is that I have the SpeedTouch configured to do NTP and SIP
on the LAN. This is firewalled and I can't find any place where I can
allow this traffic. Denied traffic is dropped on vr2 interface (this
is the ethernet port for the WAN tunnel).
Is it at all possible to allow connections from the "modem" network
(ie the IP subnet between the PPTP/PPPoE device and m0n0) to other
subnets? if so, how?

Pointers and tips are welcomed.
-- 
GRTNX,
RobJE