How to align viewports

I have setup two viewports next to each other to model a human head. I am unsure of how to get the grid lines to match up and to size the images so that they are positioned correctly for modelling.

The images (right and front) match in photoshop.

I want the grids to match up and the read and green lines to match. What am i missing?

Shft-C and C in both viewports.