Hi,
The AKB line covers a full scan,right to left,so center it side to side on the tube face using the mechanical centering magnets,disregard all other indications, use only the AKB line for reference.
After that if the video picture is not centered,use the projector position shift to move the picture sideways within the raster.
For vertical centering you could use a internal grid or even external video signal.
Yuval.