Nevin Engle says that his zephyr pouches are tight, insufficiently
flexible and are holding open the valves [110829 MMDigest].
I suggest that he replace them with new material, ensuring that he
allows sufficient slack so as not to touch the valve button in the
off condition.

The best zephyr is obtainable from Herzog: http://www.lederfachhandel.de/ 
They supply it in three thicknesses and it is very uniform in thickness
and finish, and is perfectly airtight as supplied.  It will not
delaminate.  It should be affixed with a thin hot glue and no dressing
need be applied.

Nicholas Simons, GB