I am having this problem at the moment. My ds soaks through everything we put on him. Fortunately they are not leaking but close too. We have tried hollow oak, wnnn,udnn and bedbugs all are completely saturated by the morning. Don't think it is helped by him having a
straight before bed and one as soon as he wakes in the morning.
You should also try Emma at Puddlekins (and no, I'm not on commission
). Bella has a 5oz bottle before bed and a 7oz bottle immediately on waking. Depending on if she has a cold/is teething, she can also drink 1 or 2 tommee tippee sippy cups of v dilute squash overnight too. Which is how we get to 20+oz of fluid in her nappy, and it will hold (just about!)