There has been much debate over the last week or so about the correct
gaps between the various boards within the Duo-Art expression pneumatic
assembly.  The actual gaps and the overall length of the assembly are
of secondary importance and can vary depending on the actual thickness
of the boards used, the material used and the day of the week.

The most important parameter is the movement of each section when
under suction and this must be measured at the operating position of
the output rod when each section is put under suction, modelling the
operation when installed.

You cannot go wrong if you follow the instructions laid down by Paddy
Handscombe and referred to by him in his recent response to this issue
[101009 MMDigest].  Anything more is simply unnecessary and can lead to
confusion.  I would certainly not cover the assembly in two separate
materials, thin tosh followed by leather.

Recent postings are making a mountain out of a simple molehill.  Just
keep it simple.

Nicholas Simons, GB