We're still firmly in size 4 and I've just checked old amazon orders and she's been in size 4 for a year now!! We use 4+ most of the time but the sizing is fine. She was dead chubby until she started crawling and since then has slimmed down a lot. Still on 50th percentile despite all my worries about her fussiness with food.
For leaks I find with us, no vest at night encourages leaks as nappy not held so tight to bum so potential for a gap, and also too small a vest at night makes them leak as the gel doesn't have room to expand. But we are pretty lucky as rarely ever have leaks.
We made the mistake of laughing at DD on Sunday when we saw her picking her nose and then putting her finger in her mouth and proclaiming "yumyumyummy!". Now she won't stop doing it. Urgh! You have to be so careful with them at the moment with things like this!
I am finding this a great age though on the whole, she's getting so funny. Her words are suddenly increasing too, she came out with "zebra" yesterday, and "garden" (well, darden), and then when we were cycling to nursery this morning - first time in over a month - when I got the bike out of the garage she said "bike!". When she does something she's pleased with we get "Yay!" and a round of applause for herself.
She is also spending a lot of time trying to jump... it's the most hilarious thing ever! she tries so hard and thinks shes doing it (gives herself a clap) but her feet haven't left the ground yet. I swear it's better to watch than them trying to walk!