Great review Doc

I only have one piece of input here and that's only because I've spent a lot of time fiddling with this.

Reducing the diameter of the rear piston wont help it get smoother it actually just increases the point loading on the sharp edges of the slot as seen in the diagram. The most ideal would be to increase the diameter to within a few thou of the ID of the tube. That would give the greatest bearing area and the lowest point load.

The trouble is the slots are stamped and that bends the edges of the slot inward. which precludes using a perfectly sized body.

FTP in Tube.jpg