There are several presentations on this topic available free at the IBIS Summit file archive on the official IBIS website. Mr. Arpad Muranyi has lately produced a considerable amount of material on proper generation of differential IBIS models and model data. I do not believe that S2IBIS2 covers any of these directly, but S2IBIS3 may; please check with the S2IBIS3 authors at NC State University for details.
See the files under "Author" as "Arpad Muranyi" under the following link (his presentations are listed about halfway down the page):
**broken link removed**
Please note that an updated Cookbook for IBIS, covering issues such as differential IBIS modeling techniques, is scheduled to be issued before August.
I hope this helps!
- Michael Mirmak
Intel Corp.
Chair, EIA IBIS Open Forum