I have a friend who has a Jurassic Park jeep, and he definitely needs something like this.
Sorry that the current stage isn't what you want, but you've come this far, and I have every confidence you can overcome the problems and see it through.
What I think is interesting is that you are reverse-engineering it.
For the movie, they took a real thing-- the skeleton of a long-dead animal-- and sculpted over it to imagine what it might have looked like with skin. They made him from the inside out.
You took the way their finished sculpt looked, re-created the surface, and went the other direction to figure out what the internal structure would need to look like. You're making yours from the outside in.
I think that's an extremely visual and hands-on approach. I'm impressed.
Alex