Welcome, nyartist. Please put a first name in a permanent signature line for us to use (UserCP/Edit Signature).
This the same shower project from late 2006?
If so, maybe we can get some idea what you're working on. Otherwise, you're gonna hafta give us a lot more information before we can do much for you, I think.
How high and how wide a "knee wall" should be is a pretty broad question.
My opinion; worth price charged.