Triples rule. When you can sit and spin in the middle ring on your common steep climbs, you can go to a double. Not before. And don't go to a wide range cassette trying to accomplish that. That's going backward. And even if you could, why get rid of the granny? What's it weigh? Better to have it for a bail-out. I've ridden with one (1) guy who got strong enough to abandon his granny while using the same cassette. He's on a racing team now and moving up the cats.