stretch graphic in Report Builder

Hi all, I have a problem with a chart in report builder.
I have created a table with a parent group and a child group.
The parent group has two columns, the first one shows me the value and the second the graphical aggregation.
The second group, the child, has two columns. The first shows me the value expression and the second the related graph.
My problem is that when I have more children, the parent chart gets bigger and doesn't show me the values well. an example is below.
I tried to put a rectangle with the graph inside and in this case the graph looks good, but everything moves up.
Does anyone have a solution?