Just wondering what I am doing wrong! Can anyone help?!

I have been snapping the 2 inserts for my haute pockets together but find that the large insert is just so long. My DD is on the middle setting, and even when I stretch out the elastic, the insert still pokes out the back..Is it just me that has this problem! What have I done wrong?! I use a lot of pocket nappies so I'm not unfamilar with them..what am I doing wrong??!