After looking at schedules, ILSS, MMSA, WIMS, and AMSA are done after the ILSS Memorial Race. MLS has I-35 on their schedule through the end of September (with Sept 28 as a "possible national event").

I would say September 28 (you guys with MLS - if they're even doing a national event).

This is just my input, not even saying we're coming, but we would consider it depending on the track. I can say for myself that if it's the first weekend in October, I will instead be attending Gold Crown at Tri-City. To note: Roger hasn't had much luck scheduling a race in October (with weather and cars being done).