If you do use a standard flat piece curb, you set the pitch when installing them. It's one of the few times when it's okay to install something "crooked". ; ) A fabrication shop can make them however you specify, but you'll pay extra. Sometimes you can find marble saddles or curb pieces that do have an extended bevel on each side. Depends on what the local places carry as "standard". Setting glass on a pitched curb top is not a problem. If you do plan on using ready made marble pieces, look of one with an extended bevel. A standard bevel may only be a 1/4" or 3/8" 45-degree chamfer on the edge of the stone. A "hollywood bevel" is an extended bevel, so it's a longer area of slope. Then there are "double hollywood bevels", where each long edge has a wide bevel. A picture may be worth more words, lemme see what I can find...here's a hollywood bevel Hollywood bevel: While most thresholds are 3/4" thick "door" thresholds, you could use those, or you can get the same material and style in thicker material if you want a thicker curb.

A lot of marble is very very fragile until it is installed. I think part of the problem is the proportion of the piece - almost 4' long and 6" wide, you need to support that sucker across the entire length of it at all times. Once it is installed it shouldn't be a problem - it will be fully supported and thinsetted into place. Basically it can't support it's own weight. If you are willing to pay for another one (and since this one broke while you were transporting it I can see why they wouldn't want to pay for it even though it probably should not have just been laid in your trunk) You can probably cut an 8' 2x6 into two pieces and sandwich the threshold between the two pieces and then tape the thing up like crazy so that it's fully supported. That should help you get it home. When putting it into place make sure you have at least two people and you don't hold it in such a way that it will break from its own weight. Frustrating but I hope you can get it resolved.

We LOVE our curbless shower. It WAS expensive. We have a pier and beam foundation. I don't know exactly the inches but I learned that because our shower was 5 X 5, this made it so it could be identified as an ADA compliant shower - no larger or smaller works for this label - must be 5X5. Once you are ADA compliant, rules can change and in some case are more lenient as far as the floor slope. You need to check your local code. Don't want that wheelchair toppling over, I guess. We have a linear drain on the far wall away from the shower opening (3 ft wide) and which always drains well with no water coming out the shower opening (we chose not to put in a door and not having a door adds SOoo much wonderful ambience, it is great) and though I don't know inches precisely, there is no way it is a 4 inch drop on the tile floor. Maybe beneath, it took four inches but I doubt it since no "shower pan" as such was used, I'm pretty sure just Schlueter waterproof sheets/products were used. We also had radiant floor put in to keep any possibility of drafts down in the winter. But I'm obviously not into the details on this very well and got help from Mongo on some of this so I will defer to him on the contruction details. But I would like to say most importantly that the 5X5 is a perfect size and we wouldn't really get any more enjoyment from an 8X5 but your mileage may vary. I can be using the fixed shower installed on one side of the room and easily reach across to the hand held shower installed on the opposite side of the room at the same time. Room enough for two. AND turn on the rain shower in the middle. Fun, fun, fun. And because ours was 5X5, we had space to put a closet on the other side of the wall of the shower for use in the adjacent room. Closet also gave us a place to install the Moen idigital shower valve and access panel. This really allows the shower walls to have a clean look and adds even more fun to the whole process of showering, IMO. It was quite expensive but if we had to make the choice again, we would still choose the curbless. But make sure your contractor has experience cause I definitely got the impression you want someone who knows what they are doing.

The attic is behind the long 5' wall of the tub/shower combo, so stealing space from there makes the new shower wider. Contractor is framing now. I wasn't home today to see first hand, but I think they were able to steal about 14" or maybe a little more. So the shower will be a comfortable width (about 44") and the toilet will have 32" to itself instead of 30." The ceiling had a wierd fur-down, so they took that out and now the ceiling height is 8 feet. They will waterproof the floor. I think Ditra is what my contractor prefers to use on the floor.