Curtain roller shafts wear to their support bushings, swapping top with bottom may make the shutter run slow. Excessive wear on the roller shaft or its bushing can be somewhat corrected by adding shim stock to the bushing or in severe cases sleeve the bushing. Graflex FPS require .002 to .003 inch clearance between the roller shaft and the support bushing to run properly. The adjustment plate end rarely wears.
The aperture stays are usually copper, .010 to .020 inch thick, and can be opened with a 1 inch wood chisel pressed into the gap where the curtain is/was. The stay can be crimped onto new curtain material with the flat section of needle nose pliers.
Knobs and dials of that era were attached with taper pins, large end usually at the top so they are driven out from the bottom. Some seize into the shaft/knob and require a day or more in penetrating oil to come out.
Straight on pictures are usually best for camera part pictures, side angle pictures hide details and distort the assembly.