I just found an old 1990's Phantom spindle with the "C" on the spindle. It was made for using a top pill. I put a long bolt in a vice that fit the bottom hole in the spindle then measured the spindle "C" caster difference when rotating the spindle. I did it both directions with the spindle moved toward the rear and towards the front and could definitely see a difference. Should have done it also with camber gain measurements but that's even more of a pain.