A few additional comments I could make. There are the pen&paper calculations, and then there are the real-world numbers. Looks like you are handling the pen&paper ones just fine. Now the wrinkles.
First, you are doing the math with the Voc, which is for checking max voltage the controller is exposed to. For power production, you want to be using the Vmp, which is likely to be more like 18V. So, what the controller is actually seeing as the battery charges is more like 36Vmp, not the 42Voc.
Second, the panels on the RV are mounted flat on the roof, or are they angled towards the sun? When the panels are not directly oriented towards the sun, their output has to be de-rated. 60% re-rating is a good start. The value that gets de-rated is the amperage, not the voltage. Voltage stays about the same, no matter what the sun intensity is. But, the amperage goes down as the sun makes a more and more acute angle with the sun. Same for cloudy days.
So, looking at the real-world output of four panels, what you are most likely to see on a daily basis is (400W/12.5Vcharging) X 0.6 (60%) de-rating = 19.2A. So, your controller will handle that. Suppose you park the RV on a South-facing hill in June, when the sun is at it's highest possible point. The output might exceed 20A for a short while, but your controller will just clip off the extra power. Too high volts will fry the controller. Too high amps just gets clipped off and is unused.