And a year later....
Had the stock layup complete quite rapidly after the cutting the core only to run out of time before the competition I was hoping to run it in, cue COVID and i've had no motivation to do the finishing touches with most comps canceled.
In the last few weeks i've chipped away the final fitting and polishing that i'm finally happy with the result, not a product I would put on a shelf to sell, but 100% fit for purpose.
Learnings - the model I programmed the CAM off was for a laminate timber stock, no allowance for carbon layup..... so the final is ~1mm fatter but with some careful trimming isn't too much a problem.
Glueing and clamping the two halves wasn't perfect so there is a slight kink, thankfully you need to know its there to notice and doesn't seem to effect performance.
So far i've only managed a few rounds down range but it does feel much more comfortable to be behind, i'm cautiously claiming a better fit and in that regard, a success.