Well it's good news and bad news. I took the crossbow up to the Cloth of Gold field archery club as a visitor of my mate Mick the blacksmith.
The test shots went fine and he took some video of a shot.
I then tried one shot at 10 yards to check the sighting and it kicked like a mule... the bolt was in the target about an inch low, the string was nowhwere to be seen and the right nock had sheared clean off.
My guess is that the brace height was a tad low and the string had gone over the bow taking the right nock with it. The string had then pivoted on the left nock and flown off to my left and slightly behind me, as that is where it was found.
Well it wasn't a disaster as I'd taken good old Twister with me as a back up.
Twister shot like a dream as if to say "you don't need to mess with crossbows!" I hit some great first arrow long shots, and I could tell that even with sights on a crossbow, it's all about distance estimation.
Mind I did manage to smash the points off 6 arrows! It is rather stony at Cloth of Gold. It was showering off and on and I was pretty tired, so after 30 targets I took my leave with Mick and Rob shooting on.
I shall take 1/2" inch or so off each tip and try the crossbow again, all these small changes will eventually be applied to the MkII prod.
From a structural standpoint I think I made a mistake by over doing the sanding on the back of the bow at the tip where the horn overlay is glued on. Sanding it flat makes it possible to glue on the horn but removes some of the strength of the bamboo. This time I'll flatten it much less as the bamboo has more strength than the Yew. I'll also glue some horn to the belly and file the string grooves into that (rather than gouging into the Yew belly), as a sort of string bridge/string catcher. I'll also take care to mark the minimum brace height on the track of the crossbow so that I can easily check if the string needs a few extra twists.
I've also been making a better rear sight with a sliding sight block of horn with a bit of spring wire holding it in a steel frame. I can file sight marks into the frame so that the block will slide up and click into place.