Maybe I'm missing something. It is hard to get the picture without seeing it.
I'll assume you have followed others advice and have verified the P2S.
You say that the cart is all the way forward, it hits the arc on the outside but sits behind the arc on the inside. And that the cartridge is all the way forward in the slots.
So, if you move the Mint protractor back until the stylus is on the arc at the inside, will the cart not be too far forward on the outside now? Which is ok, because you can move the cart back in its slots.
Of course after you move the cart back, you will now need to move the protractor again to align the inside and then recheck the outside again. Keep doing this, correctly, and you should find that everything is converging on the arc. Using an arc protractor is an iterative process. I think you just need some practice.
Perhaps it will be easier to start with the cart in the middle of the slots?
I'll assume you have followed others advice and have verified the P2S.
You say that the cart is all the way forward, it hits the arc on the outside but sits behind the arc on the inside. And that the cartridge is all the way forward in the slots.
So, if you move the Mint protractor back until the stylus is on the arc at the inside, will the cart not be too far forward on the outside now? Which is ok, because you can move the cart back in its slots.
Of course after you move the cart back, you will now need to move the protractor again to align the inside and then recheck the outside again. Keep doing this, correctly, and you should find that everything is converging on the arc. Using an arc protractor is an iterative process. I think you just need some practice.
Perhaps it will be easier to start with the cart in the middle of the slots?