The easiest way to set up a custom paper size is to make the width the exact width of the roll size loaded. Name it for example below 24 inch roll and size it so that the length is 10 feet (unless you have something bigger than 10 feet long to print). THEN, the most important part of this is to use the "REMOVE TOP/BOTTOM Blank areas" button that is located on the features tab in the driver:
Photo 1 shows the proper way to make a custom page setup (on orientation keep it in "Portrait" if using these instructions:
Photo 2 shows the driver "Features" Tab with the no spaces button highlighted:
