Not seeing the stern is challenging!
We bought a 53' Carver Voyager for cruising the Great Lakes last summer and my husband is completely blind to the stern. We installed a camera late last summer, but didn't get a chance to use it much. Before the camera, we relied on me being on the stern and us using walkie talkies - he's inside the upper pilothouse and I'm on the stern - we can't hear each other yell. Not the perfect solution. We're investing in head set walkies this year.
So ..... yes, its really good to have a spotter but make sure you can hear each other over the surrounding noises!