I would just tell him in the situation like that then that the controller will be moved to where the original plan for it was at.
I think that it a lot of times involved certain cutomers what to expect from them. You just have to feel them out. I usually just tell them ahead of time right then and there that the cost is going to be more (without the paperwork). Other customers I just go ahead and bill them for the extra work and they are fine with it. It just depends on the customers and the price involved I feel.