Here's the center cutout now which was the last thing I needed to do before soldering down the chip. This access window will enable me to solder the main power lines to the main pads on the bottom of the chip. The circuitboard is aimed at tying into the various perimeter pins of the chip but this window is for the high power lines on a separate layer below.

I was able to cut this window out with the highest zoom setting of my magnifier visor (I think like 20x zoom?) and an exacto knife. Quite a challenge but made it happen!