HP Designjet T790 and T1300 - Loading Media 

I know this is an incredibly old comment, but useful for anyone who happens across it. Typically you wouldn't want to print on any less than 150dpi (dots/pixels per inch). A typical print is generally 300dpi. So for the best quality, you'd divide your width and height by the DPI to find out the sizing that would work best. So for your example above, at 150dpi, you could print a 26"x14" and have it look pretty good. Any bigger than that would likely cause pixelation to be seen. If you divide by 300dpi, you can print at around 13"x7" and have it be great quality.

I get the same message as Imran, good instructional video otherwise thank you.

I have the same problem...terrible design by HP. It took me over an hour to load a roll...

@@RealJoshBinder Yea, I'm having the same problem. It's a terrible design.