[quote name='6v6' timestamp='1444647853' post='2884692']
IMHO you want something without much flexibility, as it'll help stabilize the crack.
The problem with PVA in this application is it's designed to work well between two bits of tighly clamped wood (where it'll be stronger than the wood itself in most cases) - but pouring it into a crack with no clamping it'll just end up a slightly flexible filler, with not much real improvement to the structural integrity of the crack (at least this is what I've seen with the PVA varieties I've used).
If you want epoxy which isn't too brittle, try a slow cure variety, IME these are somewhat semi-flexible (moreso than the fast-cure kind), and can be turned into a good filler with the addition of a filling agent like "micro ballons".
The other option as previously mentioned is to accurately machine a flat above the crack, then clamp a veneer with PVA so you regain the structural integrity via a solid non-cracked piece of wood, then sand to match the profile of the surrounding wood.
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Thanks 6v6 - some good food for thought. Only issue I have now is getting the old PVA back out - seems to have softened during the second stripping!