Determining Inside Dimensions & Geometry of a 'shelled' body?

Hello, this is my first post here. I have been using shapr3d for a few years now, but getting into more complex uses and designs has led me here.

I am designing a center console for a boat, which I will be building a ‘plug’ for so a fiberglass mold can be made from it. I have the console designed (approx 72" long X 40" wide X 50" tall) and it is a pretty complex shape with multiple intersecting compound curves and such.

When I shell this object to have 3/4" thick walls (it will be made from 3/4" MDF), is there a somewhat easy or automated way to determine the inside dimensions and geometry of this body? Maybe rather than ‘shell’ the body, could I ‘remove’ and copy that inside shelled piece?

Here is what I am trying to accomplish - Since this will be a plug for a mold we must build an ‘egg crate’ style plywood framing inside of it so it holds it’s shape perfectly. With the complexity of the shape, it is pretty much impossible to free draw framing members that would scribe perfectly to the shape of the inside of this body.

My thought was that if I could shell the body, leaving behind 3/4" thick walls, but retain/copy the removed center piece, then I would have a ‘plug’ that fits perfectly inside the body, from which I could design the framing from.

Thank you in advance for any help on this!

Wow, that sounds interesting, can you please share some pictures about the console?
For creating the inside body, you should create a box which is bigger than your shelled body, then subtract the two bodies from each other. The result will be a core which I guess you are looking for and an outer shell. The distance between the two resulting bodies will be the gap defined by your original body.

If you have holes and cutouts on the body, it may not be that easy like in the video, but I hope it will be helpful.