Originally Posted by Metaphor_
While I don't have anything to add to help answer your question (sorry), it's things like this which drove me to do my own tuning. It's way cheaper than using shops, less travel effort, and you know you'll get consistent results (if you screw up, you can just redo it).
When I'd get a shop tune and skied badly, I often couldn't figure out if the tune was bad, or if I was bad. (In retrospect, occasionally both were probably true!) And nowdays, I don't have to witness anyone scrunch their nose up when I ask for a 4 degree edge angle. (I only have to hear grief about it every time I discuss it with other instructors.)
While a 4 degree side edge angle is probably less than ideal for teaching, according to a friend who tunes skis for Canada's national skier cross team, most of the competitors race with a 3 or 4 degree side edge angle. Most shops in my area, if you just tell them to sharpen the skis and don't given specific instructions, will give you a 1 degree base edge and 1 degree side edge.
The tuning shop that is associated with the demo centre where I work has a Wintersteiger ceramic disc automatic edge sharpener and it does a terrific job. Because it grabs the ski and automatically makes several passes (once the machine is set up, human hands do not touch the ski), based on what is programmed into the machine, it is pretty consistent and this is ideal for a high volume shop. So the ski tech--shop rat doesn't need physical skills or years of tuning experience, he or she just needs to know how to program the machine.