I had a travertine sill put in and it cracked smack dab in the middle. Next time around I would use something stronger. Installer said it cracked due to being new construction and the house shifted. Now I am always checking the caulk to be sure no water is going underneath it. Go with something strong! I've never even stepped on this stupid sill.

My shower is an odd size and the company made a custom pan with the cultured marble material. It's a textured matte white, so doesn't look like the typical vanity material with the wisps of color and a shiny surface. Of course, a pan's practicality decreases when the area is huge and you have to get it into position! I don't understand why zero entry wouldn't work. You need about 4 feet for the drain slope, anyway. Another foot will allow for a more gradual height change and a configuration allowing wheelchair access. I wish I had the room to plan for age/injury limitations. Take a look at Elphaba's bathroom/shower. Tiled pan, large 5x5 shower, no door. I've always loved Mydreamhome's 4x8 curbed shower, scroll for her pics.

You probably have made your decision by now. I recently had a horrible experience with customshowerbases.com. Their custom service was excellent until we fully paid for the order. Everything went downhill from that point. (1) Promised two weeks manufacturing, but it took FIVE weeks to get to us. No one updated us any of the delay in the meantime, until I called. I am pregnant and due in a couple of weeks, such delays are not acceptable! (2) Arrived product is flawed with extremely low flange height than indicated on their website and even lower than indicated on our custom drawing. This is a big deal, as any flange height lower than the threshold will cause water leak....they are supposed to be experts in this realm, oh well… (3) Base outside dimension is off by 1/4", more than their promised 1/8" tolerance. This is also a deal breaker, as this creates larger gaps around the base and our existing tile floor! (4) Arrived with minor chips on the corner, which is not a big deal. With all the issues, they refused to send me a new one. If anyone is considering this company for any of their products, you know what to do....

If you need a custom pan because of an existing drain location, RSS (Revolutionary Shower Systems) makes custom foam pans. RSS shower curbs are solid foam; Kerdi curbs are not solid. RSS is in Idaho, I think, but shipping cost should not be too bad because of the light weight. https://revolutionaryshowersystems.com/