I think the reason that WEST is accused of hardness is because they made a big deal about it, and it is one thing that can be hard to get out of cheap epoxy. So their competitors cleverly turned it against them. The hardness WEST has is not required in every case, but I don't know of any to many cases where it is a problem.

I doubt the calfee thing makes much sense either, at least for bridging the parts. In that case the tow is linear and will move in and out with expansion and contraction of the materials. One thing about bamboo is that as wonderful as it is, it is still grass, not say, carbon fiber. So in theory something of a similar set of properties, say hemp, should be able to get the job done also, and if so, why bother with carbon. I made some fenders of bamboo, and because of the watery environment I finished them with WEST epoxy. They looked great, not always the case when epoxy is used in the top coat. The epoxy was a very good fit with the bamboo, sank in just the right amount, etc... Therefore I would finish the frame with epoxy, and that would eliminate the expansion and contraction problem.