I'll try that out. Thanks 
I didn't read Fraser's book but the technique described is similar to the way I play octaves now. It's incredibly efficient and effective! And deadly fast. And the easiest way I've found to play octaves because I'm not holding any unnecessary tension in the hands and arms.
But if you take his advice literally you're wasting lots of precious movement by bringing it up to your shoulder. It's not even remotely necessary to do that. In fact, your hand can be touching the keys to initiate this movement. If you bring your hand up to your shoulder and hold your hand the way prescribed, you automatically co-contract. Not something you want to do to keep a loose wrist and hand.
Instead, just play normally keeping in mind this 'grasping' motion and
feel for your comfort zone that allows you to play it easily. It's easier to practice this on the blacks to figure out the movement and then apply it to the whites. The movement is very small and probably not noticeable to anyone else.
Horowitz doesn't use this technique, by the way.