Hola Beek. To my ears, there is not a "right place" for them. Your stage always vary, when you do the toe-in toe-out. Just choose the one that you liked most. The one third flashlight is a starting point. The vertical dispersion, and horizontal dispersion is the clue. Remember that the Vistas or any ML electrostatic speaker is a true di-pole device, you have the positive transients going forward and negative transients backward. Your stage varies, as moving them only one inch toe-in or toe-out. Moving one inch, can destroy a wonderful and balanced stage. Mark the position of the speakers before you make a change... if you do not like what you are listening, you can go back to the previous nice sweet spot. If you have several positions, , then mark them with numbers, so you can go back. Do not do changes rapidly. Wait until your brain truly senses the stage and the size of the instrument(s), vocals. Have a notebook, and write your findings. Now my best advice: Just enjoy the wonderful sound of ML. Do not seek for what is wrong, seek for what it is good!!!. Trust your ears and not in specs. Specs are just another guide. Enjoy!!!
Roberto.