shorewall and tuntap

I have installed bochs 2.1.1 with Minix as a guest OS. Bochs uses the
tuntap device in order to access the local area network. I follow the
instructions perfectly and all is well until I got to the part of
trying to get the guest and the host to be able to talk to each other.
The IP address of my host (the actual physical machine and the OS that
runs under that) is 192.168.0.1, and the IP of the guest is
192.168.0.4. The device is called tun1, and when I add a 'route add
192.168.0.4 tun1' to the tuntap script for bochs, that fixes the ping
problem. However I am now stuck, as I can not figure out how to setup
up routing in order to enable the guest to access the LAN or the
internet using the host as a router. Linix kernel version is 2.4.18
btw if that helps, and I use dialup to go online. I've installed
shorewall 1.3.0 as a firewall, and it works great. I also set it up so
that 192.168.0.1 masquerades the internet connection and the LAN (via
/etc/shorewall/masq) and I have had no problems with that, but I'm not
sure how to set up shorewall to do this for the guest, and I've
already tried using the iptables command that the bochs documentation
recommends to set this up but it fails (the docs said that the
iptables command assumes an ACCEPT policy but the default one via
shorewall is to REJECT). I've searched online but found nothing.
Thanks in advance for any pointers you can provide.