Pete wrote:

My problem is that although my supplier tells me that the cedar comes
from Canada, I keep reading that it is Western Red Cedar which is the
stuff to use. I frankly do not know the difference - if there is one -
between Red Cedar that comes from Canada and Western Red Cedar.

"Western Red Cedar (Thuja plicata) grows in Northern California,western
Oregon, western and northeastern Washington, Northern Idaho. and
northwestern Montana. It grows also along the Pacific coast northward to
Alaska" (source: USDA Wood Handbook, 1953)
I would assume this includes the west coast of Canada.

I have read that the cedar is ideally dried to below 15% but I know
that whatever the mc when the wood leaves the kiln, it slowly reverts...

Gougeon Brothers says..boats can be built with moisture
levels up to 18% but in long term equilibrium may lose some moisture
which could effect structural integrity" (Gougeon Brothers on Boat
Construction, pg. 33)

I have also been told to temporarily fix the strips to the molds with
stainless steel nails, before removing them to lay the epoxy and
glass. I can see s/s nails costing a fortune, especially when I see
them lying, bent and buckled on the floor in the boatshed; and then I
have got to pick them all up! Surely there is another way??

Use large galvanized finish nails and remove them as you go after the
epoxy has set.Temporarily nail strips through the face of the
stripleaving the heads out for removal.
Also,edge nail one strip into the one below it and leave the nail in.

but are there
significant advantages over square section when using epoxy?

Advantages and disadvantages.
Bead and cove makes a tighter looking joint, provides a "gutter" for the
epoxy to sit in so it doesnt run down as much, makes aligning strips
easier and faster which results in easier fairing.
You may be able to use section molds spaced farther apart than with
square edge.
Square edge is faster to mill and uses slightly less material.
If you have the milling equipment readily available, I'd use the bead
and cove profile. If you have a power feed hooked up to a saw and shaper
it will reduce the effort of milling.

SteveJ