K4 Is it possible to vertically restrict the display?

I have a Kindle 4 whose lower 1/3 of the display is broken and displays only garbage. The device is fully functional otherwise.

To still use it for reading I would like to restrict the number of displayed lines of text. Is that possible? Does anybody have experience with doing that?

I only found advice on how to use preferences to manage left and right margins.

Thanks in advance!