RV Shower Hot (or cold) water blast

I got the 2017 Thor Chateau 22B Class B out of the hanger and worked on the shower. This is how I fixed the Shower.

It turns out that the hot water was the higher pressure so the blast when opening the dribble valve was scalding hot water.
Therefore the it was too dangerous to use the "turn the shower head towards the wall for a few seconds method.

I have a Oxygenics 26481 Brushed Nickel Body Spa RV Shower Kit installed. Much better the the original equipment piece of ****.
https://www.amazon.com/gp/product/B00AZOWSJM/ref=oh_aui_search_asin_title?ie=UTF8&psc=1

Problem: When turning the dribble valve on after 1 minute, the water was scalding hot for a few seconds until it normalized. Potentially hazardous situation.

First, installed a shut off valve:
https://www.amazon.com/gp/product/B00JQDKTUS/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1
This alone did not fix the problem, but I think it is part of the fix. If allowed to dribble, will fill the hose with the higher pressure water which is HOT.
Next, I installed a Camco 23303 1/2" Back-Flow Preventer
https://www.amazon.com/gp/product/B000EDUTN6/ref=ppx_yo_dt_b_asin_title_o01_s01?ie=UTF8&psc=1
on the cold side behind the control. This is the side with the lower pressure and the hot water would feed back into the cold water line.
That fixed it. The added bonus is that we leave the in the position for the correct shower temp and just use the shut valve.
Installation note: on the Chateau or Four Winds there is a clearance issue when installing the Back-Flow Preventer on the cold water. The hot water had clearance. There are several ways to fix it. I took the easy way out and flipped the faucet over to get the clearance on the cold.