When you are in rows/cols mode, I see that 4x2 works but 4x1 does not.  That tells me that based on your setup, 4x1 panels will not fit on your defined page size.  In a 4x2 setup (which works), the panels need only be 297x420 which will fit on the page size you defined.  When you try 4x1, the panel sizes are 420x594 which won't fit on the page so it falls back to the only way it can print 4 panels: 4 skinny ones of 1680x148.5.

So why won't 4 panels of 420x594 fit on your defined page size?  I'd say it's probably because you said you defined your page size as 420x2000 which will result in a printable area of 414.1x1984mm (the main window of Qimage above the live view should tell you this) and since 414.1mm is not enough width to fit a 420x594 panel, it can't be done.

Bottom line: if you are using 17 inch wide paper, you should be able to set the width more than 420mm so set your page size to something like 430x2000 instead of 420x2000.  At 430 width, the printer should have a printable width of about 424mm, allowing you to do what you want to do.  You need a minimum printable width (displayed on Qimage's main window) of 420mm or greater to do what you are asking.

Regards,
Mike

Once the margin issue was sorted, I was able to happily print my muti-panel image, all thanks to Qimage Ultimate.
I'm quite chuffed with the end result.

Thanks MelW.