keeping DTIs perpendicular for runouot checks

[Neale]

How about...
Set up DTI with base and support block, etc, so plunger is horizontal. That's easy enough clear of the spindle. Put DTI on bed and move carefully up to spindle so plunger starts to move. Rotate whole block/DTI "lump" slowly and carefully about the centre of the supporting block so the plunger moves across the shaft you are measuring, and the max plunger movement corresponds to perfect alignment. That might work...