Has anybody used tracking lines on your hulls to help with laylines and ladder rungs?

My crew is good at calling the layline, but if we had some point of reference it could add to the confidence of the call (not putting any in bank or sailing further than you need to).

They are used by the monohull side of our sport and I would appreciate any advice and recommendations as of placement, type of lines (would tape be OK), tacking angles to use and so on. Also I could imagine being on the trap the line maybe hard to see and very little help. What do you think?
Thank
Jon