Well done, I admire your skill with files and other hand-tools. Not a milling machine in sight!
One comment if I may; 4 x 12ba fasteners for the reverser stand seems rather on the light side, even for Titch. Is this to the original design? My Simplex for example, admittedly 5" gauge, has 4 x 2ba. My current build has 8 x 5ba. The reverser can get some loading, from the valve gear itself and also from the over-scale engine driver.