I'm very interested in the fatigue question, so if you'll bear with me I have some questions.
The impregnation is not full depth - when I grind an impregnated lamina obliquely, there are two surface layers of impregnated wood and a non-impregnated core, I'd say the proportions are around 20 60 20. The 15% figure above came from a specimen made of a number of layers of Rose gum whose density increased from 0.65 to 0.85 after impregnation and lamination. Thinking about it, some of this has to be the epoxy between the laminations. The laminae are only 0.6mm so even very thin interlaminar epoxy layers may represent a significant part of the 15%.
It it my impression from reading stuff about including deliberate slip mechanisms in fibre composites that as long as the laminae can slip over each other without any part being strained beyond its elastic limit the structure as a whole will absorb energy. Does this sound applicable or am I riding for a fall (literally, I'm expecting to ride this thing up the east coast of Tasmania as soon as it's finished)?