How can I adjust the (non virtual) frame size?

Hi, I'm trying to replicate the Frame Window > Set Width/Height with "Adjust frame size" from Window Control object.

I've tried a action like this:

void Extension::SetWinSize(int value)
{
rhPtr->Frame->EditWinWidth = 1280;
rhPtr->Frame->EditWinHeight = 720;
}

But this just crashes the runtime. I'm sure it can be done since Window Control object does it, I just don't know how.
Any ideas?

I'm using DarkEdif, but any solution from any SDK will do as long it's working solution, I can adapt it.

This would only work with "Resize display to fill window size" turned on, not differently from how Ultimate Fullscreen object works, but doing like this has some major flaws that I'm trying to avoid.
Sizing the rhHEditWin bigger than the rhHMainWin causes Steam overlay to be cropped, it's also bad for performance since it's actually always rendering a piece that you are not seeing.

Just an update, got help from Yves, this isn't as simple as I was expecting, the original function has 255 lines, but I can work with this