Simplify Grid Row- and Columndefinitions using OnIdiom

<Grid Margin="20" RowSpacing="10">
    <Grid.RowDefinitions>
        <OnIdiom Phone="*,80,60,80,*,20,30" Tablet="*,160,110,160,*,80,60" />
    </Grid.RowDefinitions>
.....
</Grid>