Slinki minkis are excellent! I honestly think they're fab, far and away the most reliable pockets I've ever, ever tried. They are very bulky though and only good for nights or summery days when they only have a nappy on.
We have a few Slinki Minkis for nighttime. Far too bulky for use in the day. But they take a good amount of stuffing and are a good fit on Ben for night. I prefer the Slinkis to the standard on Ben, I don't like the way the tabs sit on the Standard, I find the Slinkis look neater