I have looked those over many times in anticipation. But, my question really pertains to the fact the photo owner qualified the groups as being from the GS3, yet I don't see any logical way they can be used in a GS3 since the group head is exposed. I'm just curious as to how the switching works on the GS3. Either the wiring is internal to the group, which seems odd, or there's some sort of way to detect the switching of the group via pressure differentials. Obviously it's already been figured out as (a) prototype(s) exist, but I'm curious as to how it works.