Actually, the Irwin knot is a bit different than that. Howard (modrealtor) put up a great post on the knot. Here is the link:
http://www.caplix.com/pdf/Pictures/erwin%20knot.pdf
He and I just got back from a 10 day trip. I caught 5 up to 273 and had no failures on this knot tied in 130# fluoro.
I have a new favorite knot.