Welcome to ModelEngineMaker !If you have problems registering or logging in, please use the contact menu option to request assistance.
A couple of suggestions...Putting the oil grooves in a piston can raise tiny, almost invisible burrs that increase the effective diameter ever so slightly. I take the piston down to ten or fifteen thousandths oversize, make the grooves, and then finish cut to size. Any burrs formed are removed by the final cut.
Making the connecting rod in one piece might be good as an exercise but whenever I encounter such a piece I try to dissect it into separate components and make a fabrication. That's what I did on my version of this engine.As you learned, make the flats first. Drill the hole(s) before disturbing the setup so the holes are perpendicular to the flats. Then do the turnings.
Have you given any thought to how you are going to fixture the swash plate to solder it to the sleeve to which it attaches? That gave me the most trouble when I made the engine.
Nice save Prop.Did I hear a 'whew!'?