Ion-scroll with a height percentage - can't get it to work

I’m trying to get an ion-scroll item to consume a vertical percentage of the screen, but I’m having no luck.

Weirdly the scrolling isn’t working in my codepen either, so I’ve probably got something else wrong here too.

My intention was to have the ion-scroll item take up 80% of the view, with the remaining 20% left for the buttons, but I can’t figure out what I’m doing wrong. Any suggestions would be appreciated.

It doesn’t work with a percentage. This worked for what I was doing.

Set a height value in px, wrap it in another div set with a percentage value and use this angular directive to have it fill the parent div.