I am writing here rather than answering your email because, as always, you ask a question that others have asked.
In simple terms you should not use western red cedar for strucutral applications. It is nice and light and very durable. That all makes it ideal for planking hulls, especially when glass/epoxy sheathed.
However the grain is too short and the wood too soft for structural members. In other words it is brittle and can snap easily. Also unless the loads are spread over a large area (as with the hull skin) the wood will break at a joint. It is true that epoxy may be stronger than wood, but WRC is not at all strong!
Better to use douglas fir, sitka spruce or yellow cedar. Or any equivalents that your timber/lumber yard suggest
I hope this helps