Band together the mold and pour in Smooth-Cast® 300 resin. Tint the resin slightly with SO-Strong® black. Once the Smooth-Cast® 300 has cured (approximately 10 minutes) remove it from the mold.
The casting reflects perfect detail captured from the original model. Using a glue shim will leave a very thin layer of plastic flashing within the pass-through's. The plastic flashing is very thin and brittle. It can be easily removed with a razor knife, and then sanded smooth for a seamless casting.