Best diapers

I'm having a hard time finding diapers to fit my son. He's really tall. Probably close to 30 inches by now. And he's a little over 20 pounds. He's allergic to huggies. I've been using luvs on him. I love them but we've already bumped him to a size 6 in them. Size 6 isn't supposed to start til almost 40 pounds. But all diapers I've tried doesn't come up far enough in the back and they don't fit around his thighs. I'm satisfied with luvs for now but I'm afraid we're going to run out of diaper sizes. Size 6 is the last size luvs makes. So what diapers besides huggies work best for a tall bulky kid?