UIInput: how to make the iOS text-preview area take up the rest of the screen

[niniane]

I have a multi-line UIInput on iOS.  Tapping it brings up the mobile keyboard, with a 3-line white text-preview area above it. I would like to make the 3-line text-preview take up the rest of the screen. That way, the user can't accidentally press outside the text area and close the mobile keyboard. I also want the user to be able to preview more text and not have to scroll back and forth if they're writing 10+ lines of text.

How can I do this?

Thank you!

[ArenMook]

That'd be a question for Unity. NGUI simply uses Unity's TouchScreenKeyboard.Open function on line 474 of UIInput.cs.