The laser level in action:
The ST is vertical in the other plane as well (and will be tipped back to 73 degrees later). The vertical beam is lined up with the ST, the centre of the BB shell and the midpoint between the dropouts. The dummy axle is level. All good. So now I swing the ST down, leaving the laser where it is, and set up the HT:
Then I will swing things back to the right angles, get them in the right places, and check again.