Curious, were you literally controlling the aircraft for these approaches or was the FRS syllabus directed towards FO copilots being a second set of eyes/ears/SA, similar to some backseater duties. i'd see learning to go straight and level as one thing and then learning to shoot an approach to the back of the boat without previous pilot training as taxing.
interesting either way.
Hands-on behind the boat - no. Other things like helping with onstation flying, line-up, radio, etc. all the things a "guest" copilot would do - yes. That said, we did try our hand in the simulator (with predictable results) and I had a few shore T&G/landings.