I think I MAY have an answer for you. It's cheap as hell, works beautifully and is very simple.

Take a piece of thin plastic (opaque) or exposed and processed film (or anything with similar properties) the SAME SIZE as the paper you wish to print on. This will be your template.

The general idea is to overlay this on your printing paper. It will ALSO function as a border mask. Use a piece of scrap focussing paper to take place of your print for focus and composition. At any rate, Use this template to compose and focus each of the frames in place. When you've tested exposure and composition for a given frame, place your paper with the template overtop and expose. Simple as that.

Make sense?