(HELP) Modifying Resin Grail Tablet

[FuzzyDrawings]

Hi all! I've purchased a Last Crusade Grail Tablet replica. The replica has a "hollow" back and is cast in urethane resin.

I would like to finish the back so it is more of a complete piece. I'm not concerned about weight. Do you have any tips on how I should go about this, specifically if I should be concerned about warping from the thermal reaction if I apply more resin? And from an accuracy standpoint, are there any production images of the back of the tablet anyone knows about?

Thanks so much!

 

[division 6]

Probably the cheapest and easiest would be cutting a piece of insulation foam to fit then bondo the edges to fill any gaps.
More expensive and potentially messy, 2 part expanding foam.

 

[AJLoCascio]

You could try great stuff as a base (be VERY CAREFUL) and then use foam-coat

 

[Moviefreak]

I had one like that but sold it long ago. I used the expanding insulation foam, I filled in the cavity and let it expand then harden. It will expand larger than you need. Then I used a saw and cut it down and then used sand paper to shape it into the shape I wanted. I then used bondo on the back side and that allowed me to create a nice rock texture and crack details in the wet bondo. Then once that dried, I sanded it smooth a bit and it was ready to paint.