I put together a simple website with details about how I built the kernel with iptables/netfilter support. I have also included directions for getting the lan interfaces setup with static IP addresses.
Please note that the instructions for building the kernel vary slightly from what I mentioned previously, but it seems to be working. The kernel Image is not yet available for download, but I hope to have it up soon.
Please let me know if you run into any problems.
http://espressobin.exertussoftware.com/index.html