I think it is more accurate to say that the batteries take up half of the subframe assembly. Tesla has been increasing the structural role of their packs with

I think it is more accurate to say that the batteries take up half of the subframe assembly. Tesla has been increasing the structural role of their packs with each new model. In this case they optimized the battery size for range and weight, and they separately optimized the structure of the pack so that it could replace most of the lower chassis, and they ended up with a structural battery assembly with plenty of empty space.