This Is a topic I've studied for a long time. I also am I fan of Marat Safin but I'm with LeeD in the respect that Safin has extremely long levers. He can create extreme leverage with a easy swing, ( his arms are probably longer then most people's legs). That said, there are aspects of his swing you can adopt like his body turn and weight transfer.
In my opinion, you have to take in consideration the type of racquet you are using. david uses a very powerful frame, he can afford the loss in leverage by gripping high and low. Your prestige mid will require a fast long swing so you'll be better off gripping at the bottom. You also be able to whip the frame through the contact zone by making both wrists one pivot point rather then two.
What I recommend for you is this. Lead the crap out of your prestige mid at 12. As much as you can handle on your forehand. (2hbh you can wield much more the your forehand). You'll be able to hit harder and generate more with a smaller compact loop.
My tgk237.1 are made to Safins spec. It's a 33 balance 360sw 350g beast. It crushes the backhand even high in the contact zone. Try it, you won't be sorry. Just make sure you can still generate racquet speed on the forehand.