Open Baffle On-Wall mini speakers

I am designing an open baffle on - wall speaker system, as previous attempts at enclosed speakers did not work out that well. I may add a subwoofer in the end or use equalization.

At a distance of about 30 cm from the rear wall is where it sounds best.

This is an inspiration.

The other threads dont go anywhere really most of them.

Are these dimensions more or less ok for a 4 inch speaker?