When I saw the post about the vertical roller, I had many of the same thoughts that Vince called out. It also seems to me that transferring a soft slab onto a horizontal surface without distortion is a very dicey prospect!

On the other hand, one of the things I've always thought about is vertical pumills. Pugmills really do take up a lot of space horizontally that could be saved by mounting them vertically.
 I've seen quite a few really old ones in youtube videos of potters like Richard Batterham and maybe some of the old NC potters, but with the exception of a really high end semi-industrial one, they don't seem to make them for the solo potter.

I can imagine there are some issues with hopper loading, but since almost all extruders are vertically mounted I can't see any fundamental reason why they wouldn't work.

Vince (and anyone else) if you were going to redesign Harry Davis' pugmill to operate vertically, how would you do it?

Also has anyone ever made a pugmill barrel out of plastic lined concrete (for all the people that complain about porcelain corroding steel) or is that mostly a tolerances problem? (I was imagining surrounding a high PSI PVC tube with concrete). What gap/tolerance is needed between the blades and the barrel in order that clay is pushed all the way through?