I thought all ST* classes (ST,STS,STX,STU,STR) has to retain the cat within 6" of the stock location.
Tri-State Sports Car Council/Chicago Region SCCA/Milwaukee Region SCCA
Do better every run.
2002 ZX3 (daily)
1990 CRX Si STS (project)
2007 Pontiac Solstice Club Sport ZOK (autox)