George, I did some research and found the following thermal
conductivity values (Note these figures are for a standard temperature
of 25*C):

Aluminum,
Pure=237 watts/meter*Kelvin

Fiberglass,
Paper Faced=.046 watts/meter*Kelvin

So, what I should have inferred from my non-aviation experience with
these materials is confirmed by the above thermal conductivity values.
That is, aluminum is a good heat conductor-it can either gain or lose
heat very quickly. Fiberglass on the other hand is a good insulator.
It does not lose or gain heat very rapidly. Thus once "set" at a
temperature, it will tend to remain there longer than aluminum.

Therefore I would agree that versus fiberglass the aluminum surfaces
will cool to icing temperatures faster, and conversely will heat to
non-icing temperatures faster. The composite will cool more slowly,
but once cooled, will retain that temperature much longer, meaning like
I discovered this morning, my composite plane will/may be iced when the
Cessnas, Pipers and Mooneys won't.

During the preflight "Hand Checking Of All Surfaces" has added meaning
for a composite driver.

Pete