That's a tough one with a Karbon.

Here is a handy link for the gooseneck and another for the deco faucet.

The other possibility I'd suggest is the old-fashioned spigot but it's also not ideal with the Karbon.

Have you called Kohler to ask for a suggestion? I think their website doesn't always turn up all the possibilities and they might have something that's just right.

go to tapmaster.ca and get the 1771, for a single water line.
It costs about $100 less than the 1770 which is for both hot and cold water.

http://tapmaster.ca/catalog/3

This turns water on and off.

For a spout, get your stainless steel guy to solder a tube, or to leave a hole for a tube as a spout. A welded in place tube looks better.

Since you mentioned a stainless steel fabricator, I'm guessing that he is making a stainless steel backsplash, and that the ledge is a part of it all. A ledge sounds interesting. It's like a shelf. You could mount the Karbon on that. And the filtered water too.

I could show you other options too.
I have time in the next few hours, if you post more, showing more.
I have been considering what to do, for months.
I want a shelf that holds a wall mount faucet or 2. Or 3.

--

A tapmaster can be the only on/off valve, but nobody ever thinks of using it for that.

When you send your normal pressure house water into a water filter cylinder, you end up with a reduced flow. Hint hint. Since this flow is adequate, and acceptable, you no longer need more "valving" than a Tapmaster. For other peopel or for other applications, it may happen that a Tapmaster's brute force on or off switching is unacceptable, as they want to be able to modulate flow. This does not happen when you have a weak flow (filtered water line).

The thingie at the end of a normal faucet spout is an aerator, and these days aerators are also flow regulators. (you can prove this to yourself by web searching "faucet+aerator+flow" or neoperl). So, if for any reason the flow you get from your filter were to be too high, you could install an official spout sold by a faucet manufacturer as a spout (by cutting off the welded spout and drilling a hole for the new spout). ALSO, for $5 to $10 you can install a ball valve in the water line under the cabinets to throttle flow. In other words, there are many ways to skin a cat, and you can have a narrow tube as the water spout. Fridge water lines are supplied with narrow tubing, so don't think you need a wide tube. You could also use that same plastic tubing to deliver water to the spout tubing, as a tube inside a tube. (this is often the case with instant hot water spouts). ALSO, you could use the same ultraflexible teflon tubing used for instant hot water spouts as your tubing, inside any welded in place spout.

As I mentioned, there are other ways to solve this dilemma. Post again including real new information if you want more from me.

Good luck.

thanks for looking. Davidrol, I will send your message to the architect. He is the one dealing with the steel fabricator. What you wrote makes sense to me. What other real new info do you need from me? We definitely want it to be wall mounted because that is the look and the convenience we are looking for. I think I can rustle up the architect;s drawing of the front view of the sink, if that helps.

The options that I listed are all too big for the situation.

instead of posting a never ending series of paragraphs about fine grained details, i prefer to hold off until the thread takes a new direction and receives new input. That is a way for me to ensure two things related to sanity and balance. One is (a) that I get something in return, e.g. perhaps some new twists, new ideas, new views, new information and the other is (b) that I only spend an hour or two here and there instead of all my life in "being helpful" to no end.

At this point in time to the best of my recollection you have asked me for nothing at all that is specific, so it is fine if in this post I give you nothing of any significance in terms of content here.

b.t.w.
From the tapmaster site:
"What powers the Tapmaster? The water pressure that exists in the hot and cold water lines powers the Tapmaster. The Tapmaster is a set of valves, which uses the water pressure existing in your water lines to operate (hydraulically), and therefore requires absolutely no electricity. When the Tapmaster is installed the system pressurizes automatically and is ready to turn the water on and off.

b.t.w.
i'll bet your architect will love being given the mandate to draw a spout. There may have already been a billion spouts made since the days of the Roman Empire and the Qin/Xian dynasty, and nobody ever needed a drawing back in those days. Now, we've become a litigious society, and we always want to keep re-doing things until they're perfect, so everybody asks for drawings. I would say to the welder, hey, anything that you can make, with a minor bend in it.

For a visual inspiration to see a tube bent into a spout, he could look at the 135 degree angle of this spout: K-952-CP STILLNESS . You may want more bend than that. If it's welded, you don't need the round thingie at the base (escutcheon) but unless you say this to the architect, he / she might not think to eliminate it in the drawing. The shape you want is a thin thin thin tube or pipe. If you weld two tubes together, you could have a stronger spout and a spare spout too. Or three tubes. One day, your filtered water could go into an instant hot tank and that could feed the second spout. Hint hint. If you weld two together, the two tubes could be side by side or one on top of the other. The idea of welding parallel thin tubes is that you get your mechanical support from the multi-walled-ness of the 2 or 3 tubes being put into a unit all together as one. The welder might say that a single thin thin tube will one day get bumped and then broken or bent. The place where the tube connects to the backsplash is a weak spot where he will want to "spread" the base so that the backsplash stays flat and doesn't warp there.

Check into the filter you bought. Some of them give high flow outputs. Good to know now.

Hth