In carbon steel piping, "standard weight" is 0.375" wall for all sizes 12" and above.
In smaller pipe sizes, Sch. 40 and standard weight are the same. But in sizes 12" and above, Sch. 40 keeps getting heavier with increasing pipe size. So, for example, 24" Sch. 40 pipe is 0.687" wall.
"Schedule 40", if I remember right, is nomenclature from ASTM A53, which only covers pipe up through 24" size. So I'm not sure if there is such a thing as 28" Sch. 40 pipe.
The "s" normally refers to a separate, lighter schedule for stainless steel pipe. I don't remember what specification it is in (maybe A312?), but that specification may not extend past 24" either. (You can download these specs from ASTM for a fee.)
Anyway, the link above shows that 3/8" wall thickness for "standard" weight. That may be different from stainless, and doesn't correspond to a Sch. 40- so make sure what it is that you're needing.
You can also have pipe custom fabbed from plate, and when you get into 28" stainless steel pipe, it may be just as economical to do that. And in that case, you could make it whatever wall thickness and OD/ID you wanted.
Perhaps someone with these specs in hand can correct the above if needed?