Thanks for your post riphonda!
Just about to attempt this myself -- what I found under the compression post most closely resembled compost ... guessing it's been there about 10 years.
After investigating marine ply laminated into a block, fiberglass layup to height and even concrete (!), I'm leaning towards using a chunk of "live oak" for the replacement support. I'll post pictures as I go through it.
Nice to see that nasty sole/flooring _can_ be removed! ;-)