esshup,
Below is the link for the State Records
Official Kansas Fishing RecordsIf you are skeptical of that record, do you think it was more likely a hybrid that was misidentified?
It is a relatively old record - from 1982.
P.S. Personally, I think of GSF as generally larger than BG. However, I suspect this is due to observation bias based on the places I have fished.
In the larger reservoirs with both species where I have fished, I have caught many more large GSF. However, most of those were caught on larger presentations while fishing for bass. I don't think a BG of the same size would have been capable of getting the hook in his tiny mouth.
The only place I have consistently caught large BG was in a spring-fed pond where the owner had a feeder set up for his channel cats. The BG would certainly eat more of the food when the feeder went off, compared to the CC! I don't think there were any GSF in that pond, but don't know for sure.