I have both. One bathroom has 1/2" starphire the other is 3/8" I like the heft of the 1/2" even though it is not necessary (like HP in a car, after a certain minimum it really does not matter except to the owner). Hinges are designed to hold 1/2" and your designer should be able to pick the right ones. weight and width are not a problem. 3/8" is perfectly adequate so we used it in another bathroom. I guess this discussion is similar to the 2cm vs 3cm granite. 2cm works perfectly well. so does 3cm. If you like the heft, get the thicker material.

I'm not an expert in transoms or steam shower design, but I'm surprised nobody has yet said why they were invented, get installed, and are used. 1/ Steam machines make steam. More and more of it. Without new steam, the experience of a steam shower can be less and less enjoyable. New steam is needed. It actually puts pressure on the walls, and in 24hour commercial steam showers this is a big thing. But, even at home, where does all the water vapor go? It doesn't all become liquid (condensation) and go into the drain. 2/ :: Plan where it will go, otherwise it will go places you don't want it to go. A transom is a safety valve putting your excess steam into the bathroom, from where the fan exhausts it. 3/ :: Otherwise steam seeps into everything. Wall-ceiling junctions. Light fixtures. Into the attic insulation. Water vapor can penetrate anything, because it has time on its side, and the world's best solvent: H2O molecules. The opposite approach is "If you only use the steam shower for a short time and not often, who cares?" Anyone want to defend that point of view? I think there is no point building something that you "really ought not to let run". Some future user might want long steam showers, or frequent steam showers. Without a transom, you are guaranteeing that your escape route for water vapor will be confused, since it's unplanned, uncoordinated and unwanted, and your result will eventually lead to problems. As far as I know. Anyone reading this thread so far would be well advised to look more into it instead of concluding that transoms are just for fun. Many homeowners don't care much about codes or practices and will allow anyone to build anything for them. After that, it may or may not work as expected, and ultimately the homeowner may or may not be satisfied. This applied to all fields of construction. My writing this out is not to say that anyone here has been intending to do the wrong thing deliberately. Hth

Hoping not to take this thread too far off topic but since the issue of keeping shower glass clean is being discussed.... Our master bath glass shower has been in use several times daily for the past 9 years. With minimal effort it is as pristine today as it was 9 years ago. We squeegee after each shower but when I clean the bathroom I occasionally wipe over the glass with wet SPENT dryer sheets. A quick rinse and the glass is sparkling! I confess I polish all my glass, windows, mirrors etc. with crumpled newspaper for a really good finish, and I do this after cleaning the showers too. Very quick, great results. Lizbeth-gardener I encountered the same problem when I was helping my brother prepare the house he had just purchased. The shower glass was almost opaque with hard water and soap scum. Nothing would remove it until in desperation I tried liquid toilet bowl cleaner (I prefer Sno Bol), wiped on with a cloth and rinsed well !! If you try it be careful, read the cautions on the container, test a small area and use gloves, that stuff is caustic! It worked really well for us and the glass became clear again.

We chose 3/8" Starphire glass for our guest bathroom. Splurged on the Starphire glass, saved on the thickness. I have to say, that the 3/8" glass doesn't seem flimsy at all. The shower is rarely used, though DH and I did use it daily while reno'ing our other two bathrooms, and we both found it to be sturdy and good quality.