Dougdeacon, my rega300 installed on an AlexMkIII has the following geometry. Pivot to spindle at 222mm and stylus nulls are at 64mm and 120mm, which seems to be close to the figures that you have mentioned. Cartridge is a BPS. I thought that those figures might be of assistance here. I used a protractor that was published in HiFi World.
Salut, Bob P.
