First up, I needed to remove the GTN650 from the tray—spent most of the morning driving from one store to another searching for a 3/32” t-handle allen wrench. Finally ended up buying an entire set cause no one selling just an individual wrench. Removed the radio from the tray. Measured panel cut one final time, then clecoed the radio trays together and fit to panel. Looks like what I had marked should work ok. Drilled a #40 hole in each corner for a radius where vertical and horizontal cuts will meet. I used my back rivet plate clamped to the panel as a fence, then made the cut with my dremel. After the cutout was removed, it appears I will have approximately 1/8” to 1/16” to file to my scribe line. My cut left some materal, but the file should finish it up nicely—I’d rather be on the long side, cause it’s really difficult to add back what is cut off!