It'll be as reliable as the machinist who does the modding makes it. Personally, I kind of figure that RC or PTE injectors will be more reliable, and, unless the person doing the machining knows EXACTLY what they're doing, more predictable.
A very tiny difference in tolerance, and you'll have mismatched injectors. It's highly likely that you'll end up with the injectors being an oddball flow rate, making your fuel system a "one of" meaning that you'll have to do all of your own research into tuning maps and the like.
I am not, however an expert in fuel injectors. Maybe these things are predictable and easy to do, but I will still maintain that a reputable manufacturer for replacement injectors is going to produce a superior result.