I too have discovered that our tub for our extensive bathroom rebuild is peeling just as yours is. What a nightmare. Ironically, my husband and I had the same bathroom remodeled 23 years ago - shortly after moving to this property - by an acquaintance. We will NEVER make that mistake again. This time around, we have had everything re-done: floors, tile, ceiling, walls, doors, all new fixtures, soffit over the tub yanked out and the ceiling opened up making the room look larger, etc. Of course the bathtub was the first thing to go in after the new concrete wallboard and flooring. Everything else was built around it, including an expensive marble floor and tile in the tub area that was on order for at least 8 weeks after the item we originally picked out was deemed "unavailable"... Back to the tub. Once the bathroom project was far enough along that we could clean the tub and bathe in it, I cleaned it with an organic cleaner and an old washcloth - in other words - I used no abrasives whatsoever. And to my amazement, a lot of white peeling stuff the size of grains of rice came off onto the beige washcloth. I kept polishing and off peeled a piece of white paint (I guess) that was about 1.5 inches by 2.5 inches. Then a second piece came off the same size. I kept the strips and the washcloth with small grains of paint as proof of what I observed. The builder came out and said he didn't want to replace the tub because of all the work involved in removing it, etc. My husband and I were both at home for this visit. The builder looked at it and "assured" us that he would call a bathtub refinisher who would do a really good job refinishing the tub. The builder called the guy to come out to refinish it before my husband and I could really digest what was happening and come to a firm conclusion. I wanted a new tub, my husband could see the "wisdom" of refinishing it - after all, even if we have to refinish it again a few years from now, it would be less headache than ripping out a finished project to begin again. Besides the builder assured us that the refinisher was good - after all, the only thing the guy does is refinish bathtubs... My cynical opinion of that was: yeah well, how many times does one customer do repeat business with a bathtub refinisher? Fast forward one additional week while we were out of town. The tub refinishing effort had cured and I set to work cleaning the tub once again with the same mild organic cleaner and a fresh washcloth. You guessed it - the opposite side of the tub peeled off just the same as the first time. It appears that the refinisher only re-did the side of the tub that seemed to present the problem, cutting corners. I kept a sample of the peeled crud and washcloth for reference. Now my husband and I are going to insist that the builder replace the tub with a different model from a different manufacturer. This too has been a project without conclusion. The demolition began 11 August 2015. Today is 17 September 15. We only have one full bathroom and no one in my family has bathed here at home for over a month. I am tired of hotels and imposing on my in-laws. I don't think I can survive another remodeling project. This builder came with amazing recommendations, is highly regarded in our town, and did 2 expert jobs (one was an entire kitchen remodel) for some friends of ours (who were not friends or family of the builder). It just goes to show you that you can't really trust anyone. I am really curious to know how your bathtub nightmare was resolved. I do not recall the tub manufacturer, but can find out. If your bathtub was done by the same manufacturer, we could bolster one another's case for resolution. I am hoping to not require an attorney for our crappy bathtub. It has been difficult to take photos because the porcelain makes a considerable glare for the camera. I will not relinquish the bathtub peeling evidence to the builder. I have a feeling that I need to keep it for future reference. Stunned in SW Ohio

The Cook B Correct! Have to create a slope to the drain - curbless means you need to place the drain lower than the floor in the bath. Otherwise you get water everywhere. The reason this matters? You said keep costs down. A funnel drain runs less than $30. A liner drain - drain alone, for that size can be $300 or more - plus the cost to slope your floor. Have you figured out how to slope your floor? Jack hammered concrete slab to slope floor down to linear drain - curbless shower entrance is just behind crystal stone wall:

While I would also not want the same contractor ( or his sub ) redoing this, there may be a legality in that you have to give him the attempt at a satisfactory repair. Unfortunately with a tile job in a shower, that can be very difficult to avoid redoing the whole thing. I am not sure if you can have them remove all the grout and redo it with a lighter hand... Ugh This is the stuff that makes feel bad for customers....

If you Google: "LG Hi-Macs in shower," the answer is clearly yes. It looks like it comes in 12mm thickness (a hair less than half an inch). Here is their brochure: https://himacs.eu/pdf/2020/HI-MACS_Kitchen-Bath-Brochure-2020_EN.pdf