I've got the rocker towers to sit flat on the top of the cylinder head. I adjusted the spindle that runs through the towers to get them to fit:- I filed away some of the cut out on the shaft with a rat's tail file.
The spindle (rocker arm shaft) no longer pushes against the rocker tower bolts - making the distance between the towers at the top greater than at the bottom. So I no longer have the bending spindle effect I tried to demonstrate in my first post.
The rocker surfaces are now in line with the camshaft lobe surfaces.
Unfortunately they are slightly misaligned in the longitudinal direction - along the engine's length. It is most noticeable on cylinder #4:-
It is not so bad for cylinder #5:-
I'm a bit concerned that if I run the engine now I'll eventually get a groove in the cam lobe surfaces due to this misalignment.