When we had the ply taipans,We would use a 6" muffin fans??
(they are used in the back of computers or the old style printer boxs)
We would put them across the top of the inspection ports and then remove the front hatches, This woud give vetalation through the hull.
I have used them without removing the front hatches it seems to work but not as good as getting the ventalation through the whole hull
Hope this helps