AK Best in his book "Production Fly Tying" suggests a quite lower position. I have found this to work well.
Put your arms at your side let them hang, Leave elbows at side and raise forearms to be paralell to the floor as a point to start to find your own personnel
comfort zone. This my be bellow table height. By using a extension made by either Dyna King or Renzetti you can estsblish an adjustable point to put your vise stem into so you can adjust your vise to your liking. This has an added benefit
you can attach a waste troll to the bottom of the vise stem. Fishin' Jimmy