Anyone use itti bitti nappies - do they come up small size wise?

[2point4kids]

I got one to try and love it so far.
DS is 18lb so I got size medium suitable for 14lb to 25lb.
It fits him fine but its very low rise compared to normal (washable and disposable) nappies.
Is it supposed to be this low rise or do they come up a bit small and I should get size large to make sure DS doesnt outgrow them quickly??
Large is from 23lb upwards

They are supposed to fit snug and are low rise - they're designed to fit like underpants. If your DS has chubbyish legs the large will also fit.