Dynamic picture size reduction for UST-projector user

I have recently become the proud owner of the Samsung LSP9T ultra-short throw projector. The image is projected onto a 120 inch screen.
Since the projector usually replaces the normal TV, the following feature would be enormously helpful:

Ambient Mode and dynamic image size reduction - prolonged use of large projection screens (like 120 inches in this case) easily leads to the so-called “motion sickness”. This usually intensifies when the camera is shaky.

A function that would allow an optional temporary reduction of the image size, e.g. to 80 inches, would be very helpful here.
Film material that has a lower resolution can also be viewed more pleasantly in a smaller image section.
The background could then be designed with a user-specific image.