Can I cut here? (QA1 upper control arm issue)

Reducing the cross sectional area of the control arm that close to the mount by doing what you suggest would absolutely reduce the strength and integrity of the UCA.

That’s EXACTLY why I wouldn’t suggest modifications to the UCA. That’s not the place for shade tree fixes.

And what if it was made that way originally? Would your internal abacus and slide rule still disagree? I've seen stuff like that done on dirt track cars that see way more stress than his part would ever see and never failed. It's simply all in how you look at something. Not everybody does things the same way.