packing of large unframed drawings

[sarahforrest@earthlink.net]

hello,

i am hoping to get some suggestions regarding the packing of a traveling exhibition of charcoal works on paper.  the drawings install behind sheets of plexiglass, which will be shipped in separate crates.  i am currently designing the crate for the drawings, which will be constructed of mdo plywood, however i am not entirely sure of how to pack the drawings within the crate.  the issues at hand are the size of the drawings - the largest is about 6' x 8' - and the fact that they are unframed and unmatted.  my thought is to make a foamcore portfolio for each drawing, but i am concerned that the drawings will slip within the portfolio.  while the crate will be opened flat, it will have to travel upright.  also, the foamcore will have to be spliced together and i am concerned that the seam will leave an imprint on the drawings (especially if i am relying on friction to keep them from slipping).  

i would appreciate suggestions from those of you who may have dealt with any of these issues.

thank you in advance,

sarah forrest