I got my copies a few days ago and have read through both books. I particularly enjoyed Linn's rebuilding info and your "Putting her together" chapter Jeff.
I read with interest Linn's discussion of the difference in height between the piston rods and and mains and how the main rods were almost parallel to the side rods at the top of the arc and yet severely angled in the "drivers down" position. This caused me to go back and look at photos of 22 and 25 in the 30's. 22's cylinder is nearly if not right-on aligned with the center of the drivers but 25 exhibits the same "out of plumb" cylinders as today's 20.
Do you suppose that both 20 and 25 got new cylinders in 1935? Or did 25 get new cylinders in 1935 and was this even still another piece of the scrapped out 25 that went to the rebuilt 1943 No. 20?
Hmmmmmmm. Another 20 mystery.