Sizing grid to fit page.

I'd like the grid to show only the available number of rows. If there is only 3 rows of data I'd like to show only the 3 without the whitespace at the bottom. If there are many rows I'd like it to fill the page and show a scrollbar. If the grid is on a vertical layout with 100% height and the grid is set to 100% height and there are many rows then it works the way I'd like. However, if there only a couple of rows then the grid still fills the page with whitespace at the bottom. If I set the grid to have undefined height and there are only 3 rows then the grid will still have whitespace at the bottom. There seems to be some minimum size. Thanks.