4 Inches seems to be a good spacing. I have seen one with 3 inches but it was tight. It also depends on the kind of tap handles you are looking at. so I would say 10 inches will get you two or three faucets. As far as height...don't know. I don't think it should matter that much...but I might not be thinking clearly. Do you have a photo?
One more thing. I did see an install with 2 inch spacing but they used those stock small handles. The builder told me that they were happy with it, but it was hard to work with them getting wrenches in etc.
I agree with anthropod, it all depends on what tap handles you are going to use (now and in the future). I mounted mine 4" apart. The height really depends on how high you want to reach for the tap, all personal preference.
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