Great Video. I’d like to suggest the possible use of a 1/4" downcut bit. It would be long enough and would give you a very clean cutout. Since you have plenty of waste material around the cutout, I think you would have no problems using the larger bit and you would get the benefit of a downcut shearing action.
Also another idea for hold down is to use a thicker waste board and in the safe areas of the project waste, actually use 1-1/4 bugle head screws to hold it down. That would alleviate the warp concern in the center of the piece and would also hold it down flush. I use this method whenever I can.