Glyn - Have you considered a portable AC unit. I didn't want to put
the camel hump on my 57 Overlander so I bought a 9k portable unit.
Bought a piece of plexaglas and cut it to fit the front window
and cut a hole in plexaglas to duct the hot air outside. You just
open the window and insert the "glas" next to the screen and attach
the AC duct and hit the "On' switch and enjoy the cool breeze!
AC is stored in one of the closets when not in use. It is a little
worrisome setting it up but I don't have that hunk of plastic on top of
the shiny aluminum.
Jerry (in GA where you must have an AC)
WBCCI VAC