Help me understand cartridge alignment

I have a Ortofon Bokrand AB309 arm and I'm using a Royal N cartridge set up using Baewald geometry using the Feickert protractor. It's sounds awesome. I also have an Ortofon SL15 and I put it a cartridge and weighted it so I can swap it out for the Royal N any time without adjustment. The thing is, I don't have the right headshell for the SL15 yet so it can only line up like 5MM short on the Feickert. It also sounds great. So why is this? It doesn't line up with Stevenson or Lofgren. It's just off the grid and yet it's fine. I don't understand.