Kevin,
I live in the tip of Southwest Virginia, about 15 miles North of the Tennessee border and about 60 miles East of the Kentucky border. Thats got to be at least 50 or 60 miles further south than south central Illinois.
I don't really know how warm the water gets but I did measure it a few times last year and the water temperature was in the low to middle 80's. The warm temperature didn't seem to bother the Smallmouth because I could see them cruising around the pond in the evenings.
I have also heard that Smallmouth don't do well in warm water ponds. That's why I am not going to do anything in a hurry. I intend to make sure that the young Smallmouth actually do live and grow in my pond before I start taking the Largemouth out. It could be that the adults can survive better than young fish.
If I were in your position I would stock the Smallmouth, but I have to admit that I don't know how it would turn out.
Larry
