Great to see such a project, can't really rememeber seeing something similar here.
I've attempted something similar for a Victor class SSN, but never quite finished that project. One advice that I can give you from that experience is that you have to brace those frames well. Depending on what you will use to fill up the voids. I filled the voids with insulation foam (the hard board type) and then put a layer of milliput over that.
The negative effect however was only discovered later on. When sanding the frames started moving back and forth, since the foam didn't seem to give enough support. The milliput layer started cracking along the frame lines. Those frames don't have much to hold on to and being plastic they are slightly flexible. I guess you could do this, but be sure to brace those frames firmly put some straight angled pieces against them or put a horizontal piece of frame between them, would be a shame to see the cracking on your interesting and rare project!
Keep it coming, looking forward to this one
