> The ammonia cycle is capable of pulling something around a 40 degree (F)
> differential between ambient temperature and internal temperature, and
> my measurements agree with this.

I think this is not correct.  The "40 degree" comes from the Koolatron
style heater/coolers:
"Cools to 22�C (40�F) below ambient temperature"

For ammonia cycle fridges, our big brothers have big fridge/freezer
combos that are the same design.  How about a double door 9 cu-ft
one?
http://www.campingworld.com/shopping/item/dometic-new-generation-rm3962-2-way-refrigerator-double-door-9-0-cu-ft-/34425
The ice cube maker seems like a nice idea about cocktail hour.

The ammonia cycle is not the problem.  Size is the problem.  Think
this way:  Volume goes by the cube whereas surface area goes by the
square.  So a slight increase in surface area--the outsides of the
fridge--give a bigger kick to the volume.  You design the ammonia
cycle for the volume.  So the SMALLER you make the fridge, the harder
it is to make it work, since the surface area approaches the volume.

THAT is the problem with the Westy Dometic--it is TOO SMALL.  My
Dometic made wonderful ice cubes, even if they were Barbie size.  So
that part of the fridge must have been below freezing.  But in a
hot Moab afternoon, with the interior temp of the Westy at 110 F,
there was too much surface area of the fridge for the volume of
cold.

Maybe sometimes that meant a 40 degree difference but other times
it could be less.  If the overnight low was 40 degrees, my fridge
would go to well below freezing if I didn't turn the thermostat
down.

Again, the problem with the Westy Dometic is that it is TOO SMALL.

Replace it with a Vitrifrigo and you have DOUBLE the volume in the
same space, or really less since you can put a drawer under it, or
a Propex, or....  And you have double the volume with only a slight
increase in the surface area. :-)

Richard