Try lowering the windows just a bit. When you raised the cab (which helped), it looks like you didn't change the windows, so they sit higher. Drop the bottom edge maybe 1/4" or so and see what that gets you proportionally. To start, maybe just take a black Sharpie and color the bottom of the opening before making any cuts to give you a visual reference as to what it might look like. The sill should be about halfway down the side of the cab, about 3 - 3.5' from the floor from very rough paper-on-screen measurements of the drawings. But definitely, you want the bottom sill low enough to where you can stand and rest your arms comfortably on it. Your poor fireman is up to his armpits.
Later,
K