Great pics! I noticed those once on my CPS4100, but didn't pay as much attention to them at the time. Seeing these pics definitely brings back the memories and, in light of the recent lamination threads, starts making more (or less) sense.

Such walls would definitely restrict output, but do so hopefully for improved lamination. I have a feeling that the size and number of holes in those lamination walls may be related to the eventual size of the nozzle (the largest nozzle seems to have the most holes in the wall or I'm just imagining it).
As an aside, may I repost these pics on iSoaker.com?
