I was also surprised at the evenness across strings when different settings are used. I understand from Sheldon's response that the output from each switch is combined in series. However, when an individual switch combines two coils, are these combined in parallel or series? I would think parallel would give greater consistency in output level if one switch selects a single pickup and the other switch selects two.
On my Z3 I use bridge+neck quite a bit, and would hope that the middle+neck combination is a good substitute. This is the one combination that I cannot get on my Z3 (modded with a 5-position rotary switch), so cannot compare the resulting sounds. I am glad that the prototype allows soloing of the middle pickup, as I really like this option, especially when using a pick.