Here are a few pics of what I would consider decent angles for a working square filed chain. The back and down angle and the top plate and side plate hook is a little greater than off the reel square ground but still gives decent stay sharp and quicker. Using more back sweep and more side plate hook would take you towards a bit faster but tender edges. When I have about a files thickness clearance between the file and the edge of my chain clamp I know I am just ticking the tie straps with the bottom edge of the file, which is about where you want to be.
