Gravity doesn't appear to work?

I am using Cascade as a means to show a menu in a scrolling list that takes up the entire vertical space of the device. For items at the very end, I'd prefer if the menu anchors at the bottom and and then draws upward rather than achor at the top of the view, draw downward, and then get cutoff by the screen.

I've tried setting Cascade to use various Gravities, but changing the value seems to have no effect.