It's an intriguing subject line. As we cut it as close as you can I thought I would respond.

Before light rail:

With light rail:

The 1\8 - 1\4 between the faucet and the rail is sort of lost in the reflection off the faucet and on the dark wall - I think the space will be more apparent when the light backsplash goes in. That said did we cut it too close? Probably but given what my Mom paid for the faucet it is something she is happy to live with and it has had no impact on function (her dish storage is in the cabinet over the sink so she didn't want a shorter cabinet there either).

I judged mine by how easy it would be to run my hand over the faucet for cleaning purpose. In my case it was to close for comfort so I decided against the high faucet which is what I wanted.

caryscott,

How high is that faucet? I don't think I want it quite that high, so it would give me an idea how high I can go.

According to the manufacturers specs it is 15.5". I was always worried about it so we had the installer go as high as he could with the cabs but he had to have filler at the top because the soffet on the side of the L" is deep and projects over the corner door on the sink wall. That left about 18 1\8 between the countertop and the bottom of the cupboard. The light rail is 2" (cut down from 3") so we should have had about 5\8 on paper but I think the use of the bottom plate cost us a litle space.

I like eandhl's rule of thumb but this installation makes that criteria. The tallest part of the faucet is not near the light rail and I had the under cabinet lights installed so they were not near the faucet. Because it is installed so far back (the spout lines up perfectly with the drain) the neck is already sloping down by the light rail so you can clean it without catching your hand on the light rail.

Just thought I would point out that with the backsplash in (grouting is tomorrow)the space between the faucet and the light rail is much clearer. To my eye it looks a lot better.