Thanks for the pic Louise, I'm really surprised at how little difference there is. I have bought a large limited edition Itti so I will see for myself shortly, but the outlook does look rather bleak doesn't it.
I'm amazed that anyone that has a baby big enough to go into a large could actually use them though, now that DD is weaning she can out-pee the normal two inserts in an hour if she puts her mind to it, although the mini booster does sometimes get her to 3h if we're lucky. I'm pretty sure it's the water that she drinks that does it, she drinks from her mug and then about 20mins later floods the place!