I filled the hole with Waterbuffalo horn filing dust and epoxy, a fairly dry mix and it's turned out ok. It's surprising how much dust you can mix in with the epoxy, the more you tamp it down and compress it, the wetter it looks. It's polished better than the coarse raspings but not as good as natural horn.
the nock is a reasonable compromise between strength, keeping the feature and the limb length.
Mind once I've shot it a bit I may decide to take 1/2" off each limb!
It's hard to take a pic of something so small, and yes, I should have put a rule in the pic so you could see the scale... I hope you can see the slightly concave area just before the nock on the first pic, it's part of the interest.
You can also see it's a bit over cooked, bearing in mind how white Hazel is normally, lets just hope the tip doesn't snap off when I draw it! I'll leave it a few days to re-hydrate before stressing it.
I've realised I havn't actually checked the string will hold in that groove yet, but I'm sure I can tweak it as required, the other limb tip is ludicrously narrow, a mere 7mm wide, but the limb tip has been left nice and deep to keep it stiff, about 17mm.