If you have to remove 4 tiles to get to the valve, then you're removing far more of the surface waterproofing than I'm comfortable with. Especially if this was done with a modern vapor barrier in place or membrane. I'd MUCH prefer to go through the rear and affect the watertight integrity of the shower as little as possible. I don't know what brand of valve you picked, but pick the best quality that you can for this second go around.

"When we bid out a bathroom remodel the contractor told us to pick Delta or Moen. He refused to even consider Kohler due to its lower quality." This is the type of statement that contractors and plumbers make that I don't understand. I look at a lot of real estate and as a designer I tend to look at some things very specifically. Every relatively inexpensive spec house, every inexpensive tract house my sister has owned or rented, every flipped house, every on-the-tight-budget bath renovation my non-design friends do: Delta, Delta, Delta, Delta, Moen, Deltadeltadeltadelta. The two pre-sale bathrooms done to put the house I recently bought onto the market without spending an extra penny: Delta. So here I am picking new fixtures to replace a two year old bathroom and a five year old bathroom where I can pull the Delta faucets apart with my hands, and my plumber is telling me that Delta is so much better than Kohler. I realize that there are different levels of quality within brands but still, Delta being superior to everything else has not been my experience. I simply think part of it is that they only like working with what they work with all the time. My current plumber, who is a great plumber who does tidy work and loves talking about plumbing on a higher plane, almost, he's not a sloppy git her done kind of guy, says he will not put in Toto skirted toilets because they all leak. Having had Toto skirted toilets and having spec'd Toto skirted toilets for other people, none of which have leaked, leads me to believe that when HE puts them in they leak, because he Doesn't Know How to install them very well. That's fine, I will probably Not put a Toto skirted toilet in this house because I don't want white. But why not say "I don't like installing Toto toilets, so if you want one you will have to get someone to do that part of the job." Not "They are not worth the money" or "they are a bad product". I used to be in another business, and there were some things that were really outside my expertise, or I did not do that well compared to some people and I would Tell the client "This is something I would refer you to someone else for" not "This is a lousy product/procedure" just because I couldn't do it that well.

If you know the supply house your plumber used, they may have your order on file. Subcontractors often give a job name when they place orders, so if yours did and you know where they shopped (or can ask), you will likely have your exact order. I am not 100% sure, but I think that each brand uses the same valve on most of their units (except that thermostatic valves are different). I will watch your post with interest, I have to do the same in a bathroom of our house. If I learn more, I will reply.

Thanks! The problem leak is from the spout while the water is off, which we initially thought was valve-related, but doesn't seem to be now that the new valve is in and it hasn't stopped. It's a slow but steady drip. We do also have problems with a steady but small stream of water from the spout while the shower is running (and with a small stream of water from the shower while it's not supposed to be running) but those stop when the water is off, so I'm less concerned about them.