Bob Carnie's method is closest to your original plan and does sound like a great exercise.

If you decide to go with three prints mounted together, the way to line them up is to put them on a light table, so that the adjacent images overlap, tape the edges temporarily with drafting tape, then cut through the two adjacent prints where they overlap using a straightedge and X-acto knife, and then you can drymount them so the edges butt against each other.

This presumes that the prints actually line up (camera mounted with lens node over the point of rotation, lens not too wide, even illumination of neg, etc.).