I'd still be inclined to try the next size up in Huggies. DD has only wet through when she needs the next size up and like you, I've often thought they'd be far too big on her but it's always worked. We've often had the next size up for nights only and the smaller, more accurate size, for day time.

DD is 20 months and 11.5kg and has just moved into Huggies Walkers which are the 13-18kg size. It's worked a treat again, no more wetting through.

Give it a go, hopefully it'll work.