I'm sure I have done the beeswax thing with the neck screw holes before - but this has been a long drawn out build and I must have completely forgotten. I'll not forget next time !
Looking at the guitar this morning, Simon's crack stopper is not going to work because the crack comes right to the edge of the plate - a small hole would be visible. However, the cracks do appear to be settling back as the guitar is drying out.