I think the reason this isn't normally done is due to waterproofing issues. Generally when you get a tile guy who knows what the heck they are doing to build a shower with a bench for you, they build the bench INSIDE the of the shower pan out of masonry (CMU most of the time) and it becomes like one big monolithic unit. If you are doing this with a shower base, you obviously can't do it that way. That said, I had a similar condition, just not the neo-angle shaped shower base. I did not want to deal with 1) finding a competent tile guy who I trusted enough to build a second floor shower base for me after we gutted this bathroom due to a leak in the first place and 2) deal with having to clean grout in the shower base (in my experience it's the grungiest part of the shower) but I did want a bench. What I did is probably not approved by all of the tile guys on john bridge, I'm not sure what the ones around here will think, but I think it will work. We basically built the bench out of regular 2x framing, sheathed it with 3/4" plywood and then 1/2" durock and then waterproofed the whole thing with Kerdi membrane. It's pretty much rock solid though. The bottom of the bench acts as the 4th wall, and then it turns back to make the bench and then continues upward. I don't have great pictures, but here's the best one I have: I don't think this is a smart thing to do with anything other than kerdi for your waterproofing - the chances of a catastrophic failure are just too high. I think the big thing that tile guys might disapprove of is the potential lack of rigidity of the wood frame bench cracking the grout and/or tile. I don't know if this is an even bigger issue with larger tile, I'm sure someone will weigh on on it though. I just know the princess (moi) wanted what she wanted and this was the only way she could have it ;). We just overengineered the heck out of the bench. BTW I saw a neo-angle shower with the bench at once side in a display at an Expo store once and I thought it was the nicest neo-angle shower I've ever seen.

Those GRIF form bases look really cool! I like our Corian counters in the kitchen, I think Corian would be an excellent choice for a shower base. We installed a Swanstone base in our shower about 3 years ago. It has been very easy to maintain, but I guess I can't speak to long-term durability. The shower is used every day, currently by 4 people while we remodel the other bathroom. I'd say it still looks as nice, today, as it did when we installed it. I like the raised non-slips more than etched (our new Kohler Villager cast iron tub in the other bathroom has etched nonslips and they feel like chalkboard to me -- I'll probably stick the bathtub mat over them when the remodel is done). I'd go with Swanstone again if I had to make the choice. We also have the Swanstone solid surface shower niche, and that is a piece of cake to maintain.

They were super nice and accomodating when I sent in a request through their contact form with my questions. I didn't know they made 96" panels, had a corner seat, or bigger niche with a shelf until I asked. Also providing a "remodelers" trim that allows you to put the panels over existing tile is a huge bonus if you don't want to do a tile tearout. I think they thought of everything so wouldn't be surprised if they do your dual threshold. They sent me the following details on order fulfillment and shipping: "Once an order is placed, it will take 2-3 business days to fabricate and 2-3 business in transit from our Utah factory to get to Denver. The materials are fairly sizable, so they will be strapped to a large pallet and sent on a truck as an LTL shipment. The carrier will call you before making the delivery. They will arrange an appointment with you to make the delivery. You will need to be home to receive the delivery. They will drop the pallet at your front door or in your garage." Made in the USA is a huge plus so there is no delay. Also when I called to place the order we talked to the guy and asked about what aspects people had trouble with on installation and he walked us through his tips and suggestions. We had already watched all their on-line installation videos and read the instructions. Everything seemed doable and was well described.

GN, not helpful. I don't know why you bothered, but I hope it made you feel better, bigger, stronger, or whatever. I have used the internet and have searched for weeks. No one has a double threshold on their web pages except for custom bases.