You can build any plan with or without either inside or outside stems. I like to use inside stems because they give you a better gluing surface, it seems easier to keep the stem straight and true and it fills the acute inside angle in the ends which you would have to fill before you can put any reinforcing glass strips down. Might take a little more time getting set up to strip but seems quicker and easier stripping.

I also like outside stem pieces, I like the look and it does seem easier to clean them up after a beating. Glass over cedar stips ends seem to need a bit more tlc to clean up. There's no reason that the shape of the end result would be any different or any thicker than without, the stem piece is planed fair to the strips.

Jim