Detention Question

Just bought a hopper and am in the process of reinstating my authority. Now, before y’all tell me how crazy I am (my wife reminds me daily) I’m only doing so because I have a customer that I would be pulling for direct. We have a good rate set and an agreed on fuel surcharge. The thing I am looking for advice on is what should I put in my rate request for detention. I was thinking in the neighborhood of $100/hr after 2 hours of any scheduled or rescheduled appointment time. I don’t want to offend them by asking for too much, but also don’t want to leave myself short.