On both. I fixed it by putting it in another container so we have:
Form <- BorderLayout
Container <- Center constraint, also BorderLayout
WebBrowser <- Center constraint
Then it works as I'd expect and fills the space. If I put the WebBrowser directly in the Form's Center it has the white space on the simulator and Android at least.
For FacebookAuthentication the form is generated and doesn't have this extra conatiner and DOES have the whitespace at the bottom.
Cheers,
Nick