Render gantt cell full height


I’m using Gantt Professional version and would like to know how to make it render full height (Please see the attachment)

You can see an empty space at the bottom of the gantt where there is no task,
I would like to know how to make gantt render the cell line for an entire space.

right now it can be done either by setting some kind of background image to the gantt area, or by using static_background mode and expanding auto-generated background png to 100% height
Here is a demo