Plumber's crack

We bought pull-up diapers for Pontus but there seem to be some issues with the fit, because every time he leans forward we see this:



I am pretty sure I shouldn't be seeing that much butt cleavage.

So either we change back to our tried and trusted diapers or I get him a butt bib from buttbibs.com:



Just when you think you have seen it all...