Hi Tom,
Looks like that does the trick. Thanks a lot!
In 3D printing, one could fill the entire internal space with printing material,
but typically one just fills the empty space only with some kind of lattice framework,
while printing multiple layers of material for the walls of the outer surface to ensure durability.
If there are structural features *inside*, it seems that there is no way for 3D model slicing softwares to distinguish this reliably (at least I couldn't find one), and they create multiple layers of 'walls' inside as well, ending up wasting time and material. To illustrate the difference, I attach a screenshot of a slicing software (called Ultimaker Cura) where I show a cross section of two copies of the same protein model, one with the trick applied (left) and one without it (right).
Thanks again!
Best,
Sungwook