Bulkhead replacement material

[Mike16]

Hi all,
I am new to the forum. Owned a CP16 (1976 model) for round 20 years. Knew the births were going but the stringers seem strong. I was surprised to see the bulkhead that holds the compression post soft. I guess that platform which is fore of the post is called a bulkhead even though its horizontal with a short vertical aspect. Any corrections to my terminology welcome. The post broke, maybe in a grounding, but it came loose. ( Thanks to wake boarding boats throwing a massive swell at the ramp. )
Planning to use Marine Plywood (3/4") and epoxy to wet in, coat and glue to hull. It seems the edges will need to be cut at an angle to fit properly.
Any advice on dimensions alternate materials? Looked at nidacore but I'm not sure if it is structurally sufficient. I plan to add pics once the project starts.

Also is this the proper category for posting, CP16 or should it be in DIY?
Thanks

[Mike16]

These are the dimensions from a tape measure. Like a rough cut.