Simply put, don't add an ITR rear bar if you have 350lb front, 400lb rear springs. There weren't any roll bars front or back before, then I put the ITR bar on. Big 9.5 slicks up front, and 8.0 slicks in back. The car rotated before, but.... it's an ITR rear bar. Anyways, long high speed sweepers were sideways, tight corners were sideways, wait, it was everywhere SIDEWAYS. And scary unstable over humps.
Long story short, BAD combo. But fun. Not fast. Just thought I'd share. I've swapped springs front to back, which was the original plan, to add front roll resistance. I'll get back to this later.

 

Add a front bar to counter-act some of that increased rear spring rate. That bar probably makes your effective rear rate about 600lbs.