Is it possible to ignore ScreenPercentage in a postprocess material?

I’m wondering if it is possible to create a postprocess material that gets rendered at the final screen resolution instead of at the lower resolution my game is being rendered at via r.ScreenPercentage.

I’ve tried adjusting the Blendable Location, but no matter what I set it to it seems like my postprocess material is still operating in the low-resolution space and then getting upscaled. My project is using the desktop Forward Renderer.

If not, is making a UI widget the best way for me to achieve this?