He does basically what I am trying to do with my rankings.
Uses pt differential, then adjusts for strength of schedule, and home road dichotomy. He then averages in a team's recent play with their whole season play. He uses 3.5 as the adjustment for all home games.
I'm trying to factor in teams rest into my equation as well.
You can get a rough sketch of pt spread with his ratings if you the adjust for site and rest of the teams.