I have an Atwood water heater in a Class A Berkshire. It's the third water heater the first two were Gerard gen 1 and 2. I have had my struggles with water heaters.
My Atwood was fluctuating between hot and cold during a shower getting so hot then when turning it down it would turn off the heater.
I started to run hot water in the bathroom sink and that really made the shower great. I then removed the shower head and tested the temp. I found I could adjust the temp of the water easily. There was enough flow to allow a nice steady temperature.
I then needed a very high flow shower head. I ordered this one and it works perfectly. The problem is it's a bit large and there are two heads. It comes with a 3 way diverter so it can run one or two heads at a time. If anyone has a good idea on a shower head let me know.