I own a Lauter player, though it has been quite a while since I rebuilt
it.  The wind motor works exactly the same as the common pneumatic
player motor: pouches simply take the place of bellows.  I think of it
as an Aeolian motor with pouches instead of bellows (similar opposed
"see-saw" design).  The "seal and turn backwards" test should work
fine.

If the lines are correct and the valves working properly, the pouches
can only release vacuum when the slide valve moves toward the opposing
pouch.  The valve will then evacuate the opposing bellows, but only
after it is clear of the opposing pouch hole.  Thus, if the slide valve
is the correct size and the holes properly placed, an evacuated pouch
cannot 'borrow' from another pouch.

Regarding slide valve play: The slide valve is always sealed by the
vacuum, not by the tightness of the guide pressing upon it.  The snug
valve is somewhat more likely to leak because it is not as free to be
sealed by vacuum, so it is best to have a small amount of play with
slide valves.

I wouldn't worry about the sizes of any ports, unless they have been
altered from original design.  It's usually always best to stay with
original design, especially with a high-quality player action such as
the Lauter

Craig Roothoff
Escondido, Calif.