Most hobby grade twist drills are long enough to reach in from the end of the car to drill through the body bolster. I use either #72 (.025" dia.) or # 71 (.026" dia.) to give a bit of rattle room. Casting resin is soft enough that it will drill with a "D" bit; a round rod with a flat ground to 1/2 it's diameter on one end. Most well stocked hobby shops carry straight lengths of .025 piano wire, so it's easy to make a drill four or five inches long  to do the inner cross bearers. The long hole through the body bolster will stabilize it; Schuyler's method will put it spot on if needed.. I run it with a variable speed motor tool.

Dennis Storzek