pajmon,
Okay... I did have this successfully working on version 7.1 and I did use my notes (shown above) to build a new custom-template and I know it worked just fine. Sadly, my notes trailed off...incomplete, but we did have this running at a public school before they purchased a router to handle the NAT.
So here is my offer. If I can spare some time I'll give you a hand with this and we can write up the notes. As I recall my methodology was to look at the the notes from people doing this on version 5.x and 6.x. That listed out the obstacles pretty clearly. Things should be simple from there.
Charlie... sorry for the delay. I was on vacation last week, but if pajmon and I build this I'll document it.