Increase height / remove scroll on megamenu sub menu

Hello.
Is it possible to increase the height of the sub menu in the megamenu to fit the sub menu items so it doesn’t display a scroll bar?
So, I need the megaemnu – sub menu to no have a scroll bar but instead adjust to the height of the sub menu items.
On one mega menu I have 8 menu items and on another I have 9, both of which have a scroll bar.

I’ve tried this:
.block-mega-child-cats{
max-height: 100%;
}

which works on FF and Edge but not chrome or safari.

Any help gratefully received.
Thanks

Hello.

I’ve think I’ve solved this. Or at least got a good enough workaround.

I set max-height to 500px rather than 100%. This means the sub menus fit to size under 500px height then introduce a scrollbar if the menu items are more than this.
This works OK for me so far.

Thanks all the same