Thanks for this old thread. I modified Bill's design a tad and wanted to share in case it helps someone else. I pinned the two corners along the cross cut line with a single screw, and used a scrap of T-Track on the third, so now its a miter crosscut jig.
Since I have a small shop, a small table saw, and often want to break down partial sheets indoors, I made it for cross cutting only up to 3ft. I can extend that with a straightedge for longer cuts. I need to make a new extension straightedge with a dogleg to help mark the cutline, like Sky suggested.
Without pictures... It didn't happen. :no: