For a template at 1200 x 1800 px, requires that 1" circles (300px in diameter) be evenly spaced at 75 px horizontally between circles and 50px vertically between circles (this all being at 300 dpi).
If you set your dpi (dots per inch) at 72, a 1" circle will be 72px. Make sense?
Images print best with higher dpi, in case you didn't know that.
Vertical guides are set at 225px, 600px, 975px
Horizontal guides are set at 200px, 550px, 900px, 1250px, and 1600px
I left 3 individual paths for the top row so you can create your larger circles easier.
Enjoy the file!

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"In order to attain the impossible, one must attempt the absurd."
~ Miguel de Cervantes