My 8week old is coming up for 9lb and we've found quite a few reliable nappies. Flips are great with the stay dry insert and a LL bamboo booster. They'll last a few hours but don't seem too much of a 'waste' if he poos in at after 1! They're not the prettiest, but a bamboozle stretch or a LL Bamboo with a thirstie wrap will see him through 7 hours- and he drinks like a fish and pees like a good un!! BG v4's and rumparooz are other good options
he doesn't fit his easyfits yet but the teeniefits are still good. hope you find something that works well for you!