A big thanks to David Fisher aboard Kalitsah (A30 # 440) for the heads-up regarding the potential leaks from the dorade box into the liner. I cut the dorade box off the deck and could see where it had indeed been leaking into the liner. I will refit the area and seal it up well and replace the dorade box with a hatch.
Tonight I got to it and drew the hatch cutout onto the deck with a pencil and rough cut the straight lines with the Fein Multimaster tool. The radius corners were then shaped by using a ZEC grinding disk in a 4-1/2" grinder turned on its side. Those disks remove a lot of material very quickly without gumming up the disk. The hatch dry fit well and now there is a little hand work to be done before the trim ring is fit inside and the deck can be sealed and prepped for bedding the hatch.
Sealed and fairing coat applied