Well when you can show him that precise control of the nozzles and sections can literally save chemical and money, maybe he'll go for it. Just like auto steer has become second nature to us, I'm sure he can get used to automatic section control as well. It sure has revolutionized our operation just to have what we have!
Relating to what Brian said about PWM nozzles, even with normal nozzles, spray rates are dictated primarily by pressure. It doesn't matter how many sections or nozzles are turned on, if you maintain a certain pressure, you'll get a certain gal/ac rate at each nozzle. But of course no one calibrates their nozzles, so as they wear, things do get out of spec and most guys never know.
What beerwiser said about separating the flow sensor and the valve makes a lot of sense. I think I had my flow sensor about 1.5 ft from the valve. I tried it on either side of the valve and still had problems! I guess I need a better test stand than my bath tub. Next year when I have a nice heated shop all winter, I might give it another attempt. Having a general, open source rate controller is another piece of the replacing-proprietary-technology puzzle. Be it liquid rates or shaft speed rate (a drill). It goes hand in hand with what AOG does and the next step once you get a functioning rate controller is variable rate. Every section really needs its own rate controller. Even if you do per-nozzle shut off control, I think having a 10 foot group of nozzles controlled overall by a dedicated rate controller is probably sufficient.