I've not done this, but what you might try is to print out a paper version of each about the same size and gently stick them on with a loop of tape on the back and try to get the positioning to where you like it when you stand back and have a look, then maybe do a loose outline, or just mark a few points, with masking or painters tape, pull the paper decals off, and apply the real ones as you've marked. Would that be doable?
