Washed the inside of the the existing depthsounder to remove any amine blush.
Ground out the inside of the depth sounder hole using a Ryobi angle grinder borrowed from TC Williams.
Vacuumed out the area and cleaned before fiberglassing.
Filled the hole with thickened epoxy. Filled the dished out area with three layers of 1708 .
The section appears in the photo below. The yellowish section is the natural color of fiberglass without paint or other material. The rest of the image is darker due to the filler applied to the outer surface of the hull. The left side of photo below is forward. The bottom of the photo is the partial bulkhead supporting the inboard end of the starboard settee.

Spent two and half hours longboarding the port side from the forward jackstands aft and round the stern to the midships jackstands. There was a lower section of the starboard aft portion of the hull, about twelve inches by four inches, that must have been quite shallow. Watched the extent of the lower section shrink to less than an inch wide as longboarding proceeded.
Spent a bit of time longboarding both sides of the forwardmost bow. Fairer than before. Some low spots remain. Additional filler will be required.
Entire hull has been longboarded at least once.