Thank you for your quick responses! I actually already did this with the walls, floor, etc. in my level because of speed.

My question is, does the framerate slow down at all just by the block's existance in the first place, even if ALL its surfaces are "none"?

In other words, say I have a square room with a giant crate in the center. The crate itself is an entity. I want the crate to cast a shadow using blocks, and so I create an invisible block around the crate to cast a shadow around the room. The block that is on the crate is invisible, but it DOES cast shadows. Does this make the framerate any slower than if I had never made that center block over the entity?

Thanks again!