So, you purchased this questionable product and then hired someone to install it? That had never seen it? Or helped you to pick something actually suitable for the situation? And then things were complicated further by the fact that your architecture made his original (very sound) choice to approach the install from the rear not work? Cutting the hole bigger in the tile seems unavoidable at that point.

Next time, talk to the plumber before selecting the product. What you picked is a poor choice and installed as best as it can be under the circumstances. The hole doesn't need to be filled with anything as long as the fixture is sealed to the tile. You still have the old stuff in the walls. And it won't last forever.

Thanks for your reply hollysprings.

Not that it's critically important now but had I been informed of the additional tile work that was needed I would have planned accordingly and maybe not had the panel installed. Additionally, when the plumber came out to the house after I had sent him pictures of what the job required, he informed me that he had done many shower panel installs and it was a fairly simple process. I informed him that if it was an issue, I could continue to live with the current shower setup and was not married to the Pulse shower panel and could return it to Lowes. He said it would be fine, assuring me multiple times.

Since I have never had this kind of work done before I was under the impression they would seal any openings. This was my mistake for not asking more questions when he came out and waiting for after the install was done.

Given the circumstances, you are correct in that he did do his job as best he could...I just wished he would have communicated the tile work portion. In other words, told me that there was additional work that was required to get it right for me as the homeowner. Regardless, whats done is done and I am currently waiting to hear back from a few tile contractors to seal the openings. My concern is resolving the issue instead of blaming the product choice, plumber or architect b/c again, this doesn't solve the problem at hand.

Furthermore, I contacted the shower panel manufacturer and they told me that there should be stub-outs that protrude out of the tile by an inch or so just in case there are future leaks.

After I have the tile guys come out and take a look to see if they can do the job, I will have a plumber come out and install the required stub outs (per the instruction manual I gave the plumber who installed the panel) and then tile around it. I believe the Flex supply lines are part of the shower panel and per manufacturer should never be inside the wall but instead outside connected to stub outs.