I've mentioned it a couple months ago, but now I'll go into more detail.
Long story short, I feel that this whole big body casting idea for Model Y's is a bad idea.
Now, I am sure it is great from a production / parts count / cost reduction point of view. Fewer parts to assemble, it goes together more quickly, get more cars out the door, and greater corporate profits. And the car may run and drive as well as any other.
But the bad side comes in terms of how hard it is to repair the vehicle after an accident. Sheet steel bends. Castings BREAK. Like glass. Castings do not flex.
In most minor to mid size collisions with a sheet steel car, It's not too hard to determine where the damage it, put the car on the frame machine, pull it back into shape, and cut out damaged parts and weld in replacements. Now when you have a car made of castings get hit, you're going to have a shattered casting. Pieces will be broken off here and there. There can be cracks in the casting a couple feet from the point of impact. All these cracks need to be found and dealt with.
Depending on the metal alloy, fixing them can be easy or hard. I used to do a lot with Chrysler cars of the late 60s and early 70s, and salvaging / repairing cast iron engine blocks and heads was always a delicate issue, because even if a cast iron crack could be welded, which was already tricky, you had to trace it down with magnafluxing, find the absolute very tip of the crack, and drill a hole there to stop the crack from spreading further.
I know aluminum is easier to weld, but when you've got an entire rear section of a car all cracked up, how long will it take to go from "fix it" to "total it"? I think not very long.
So I think the whole casting idea is okay..... until some accident happens, then a lot of insurance companies will be paying for total loss accidents that could have been fixed in a sheet metal car.
