One important rule of business, which I admit is very difficult to adhere to, is to always under-promise and over-deliver. That's how you get happy customers. He if straight up gave everyone an estimate of 6 months for a harness to ship, no one could complain. In fact, they'd be happy when they got it in 5 months.
Second, if Pez really has that much business that he can't keep up with it, he needs to hire and train more employees to fill the demand. However it sounds to me like he can't afford to do that, which implies that his prices are too low. If he raises his prices, demand for his products might go down, but he would make a lot more money per hour and would be able to offer a reasonable turn around time, which is a win-win.
Not trying to give out business advice but... I guess I am lol.
