Grado Ref Sonata alignment on Rega arm?

If you believed your teachers in that "there are no dumb questions," which angles of the coffin-shaped Grado Reference Sonata do you make parallel with the sides of the Rega tonearm? Both front and rear of the cartridge is possible.

Yes, I'm coming from a Maplenoll tonearm, where you just bolt the cartridge in, and it's aligned. Voila.

Any help would be much appreciated.
Never mind. Got it sussed. It's BOTH planes. Crazy.
I ignore the position of the cartridge body, which is irrelevant and more or less impossible to set correctly by eye, and align based on the cantilever (I used a Mint protractor.)