Was able to get up in the boat after work while I had daylight.
The highest objects that are under the deck hatch are the gas sending units, which are 1 3/8" underneath the lip of the hatch. This would explain the 7" circle spots that had a center point 1.5" higher than the bottom.
My father helped me identify what was used before.....bulsa wood/core! I think that might answer some people's questions whether this was original or not. I am now leaning to think that this was done before.
I am thinking that I may sandwich a 1/2'" & 3/4" marine grade pieces together, and that creates my core. I will have cutouts on the 1/2" piece to leave space for the leaning post washers/nuts, and cut two holes to leave space for the fuel sending units. This will fill the entire void back up to 1 1/4", and will leave space to resin/mat the top surface back to that 1.5" mark. The more I thought about it, I want it back to 1.5" depth. It will get me essentially resting on the retaining walls for the gas tanks, and I doubt I'll ever have to worry about this thing getting soft again.
Took a few more pics, first one is of the stern area of the boat. The others are after sanding the deck hatch down and letting it dry out for a day. It's definitely a lot dryer in general than yesterday. I have cold temperatures working against me in NE, so I may have to invest in a space heater soon to continue progress.
Few pics of where I got a little chizel crazy. Nothing that can't be fixed but definitely a
moment.