Slower Clock Speed for Testin

We are thinking of making our own product based on the BBB. One of the decisions we need to make is the speed of processor that we can live with performance wise.

I have a BBB board and our application runs great on it. I would like to slow the clock speed down to see if we can to with one of the cheaper processors in this family. How can I slow do this? We are running the 4.1 android port for the Chipsee 7" CapTouch LCD. I am hoping it is something with the switch on the BBB and not something I have to do in software, but if it is something I have to do in the software build, I can give that a go with good instructions.