That's what I love about our craft, there's so many ways to do it.
I have a slightly different philosophy concerning blade fit because of all the coated blades I work with. The coating makes for a heavy drag on the leather and if its a textured coat it will actually start to sand the leather down and/or wear on the coating. One company used to have a desert tan coating that was very frustrating, the stuff was exactly like sand paper.
Most sheath welts I do use a method taught to my by the late Dave Cole. He taught me to match the welt as close as possible to the exact blade thickness and only trim it a bit at the last 1/4 to 1/2 of the blade length. That way when you tighten the thread as you stitch it will compress the leather in the welt so you have some squeeze to work in as the sheath breaks in.
I have had some customers actually ask that the welt be over sized so there is no rubbing. This is something I dont endorse, but on a fragile surface treatment like bead blast, I guess it helps keep the shiny spots from showing up.
Again, this is not to say any particular way is wrong, there is just more than one way to skin a cat.

That, and I love arguing with Paul.
