Cut the hole bigger. You have plenty of room. As long as the trim seal can still make contact you are good. Most plaster guards are 4-5" diameter.
Thank you, I think I will have to cut the hole bigger than strip off that silver piece. I initially made this post to try to adjust the rubber thing (thought this was apart of the valve cover, my mistake for naming it wrong) to get my water temp right because it was either too hot or too cold. But I figured out how to get to the rubber part and after multiple attempts of adjusting, temp is still too hot or too cold. So, it looks like I will have to take that silver piece out and take out the old valve cartridge and replace it with a new one. Does this sound like the right thing to do to try and get a better water that just-right water temperature?
All other faucets and showers in the house we can get that just-right temperature.