Problem getting TextLiquidFill to go to completion

I'm using TextLiquidFill to do a banner heading in the appbar.

However, I can't get it to fill completely - there's always a bit of the top of the text missing (see screenshot)

Here's the code:
child: TextLiquidFill(
boxHeight: 500.0,
boxWidth: 600.0,
text: 'HELLO THERE FOLKS',
waveColor: Colors.red,
loadDuration: Duration(seconds: 4, milliseconds: 320),
waveDuration: Duration(seconds: 1, milliseconds: 000),
boxBackgroundColor: Colors.white,
loadUntil: 1.0,
textStyle: TextStyle(
fontSize: 24,
fontWeight: FontWeight.bold,
),
),

Is there a way to get the animation to stop and fill the text? I've tried adjusting the Load and Wave durations, but there always seems to be a piece missing off the top of the letters.

Thanks! :-)