I said the drives are totally exposed because the method you used is mainly used to prevent the rotational and seek vibrations to be transmited to the case. It doesn't help much on cutting down the whine from WD drives. I have the same drive as yours, a WD1200JB and holding it in my hand or placing it on top of foam I can still hear it whine away. Look around this forum and you'll see this happens to almost every WD owner. The only way to effectively silence WD's is to make custom carving rubber enclosures and other exotic materials. That's why I was surprised how you were able to silence 3 WD's by just decoupling them from the case. Maybe you're much more tolerant to noise than most of us here?
And you keep saying 'form' here and in the other post and drawings too. You do mean 'foam' right?