My little brother is getting a CNC lathe to start doing some sideowork. My unlces machine shop is getting swamped. If he manages to get it, them extensions would take no time to machine on a CNC. That flat spot tho, have to chuck it in a mill or grind it in. To keep costs down, I wouldn't put it in, I'd let the customer grind it in. It would take another machine and setup time. That would add 15 minutes to the machine time. I dont know the going rate of labor/machine time but that 15minutes could cost an additional $15. Maybe do it as an option.