I did it.. it worked... http://prntscr.com/dlwm8p
It looks kind of offset but it is OK i guess... Also, when I was changing "<grid depth="1" name="inventory" rows="4" cols="8" pos="3,-3" cell_width="75" cell_height="75" controller="Backpack" repeat_content="true" > To
<grid depth="1" name="inventory" rows="6" cols="15" pos="3,-3" cell_width="75" cell_height="75" controller="Backpack" repeat_content="true" >" I noticed I had cell width and height "67" instead of "75. so I changed it to 75 as well.