wrt roll paper sizing, I think I would set it in the driver to a long length, arrange images, then go back to driver and set the length determined by qi.
I think the point Joost is trying to get across which is one I come across using my HP Designjet 130 is if you set the page length long then use optimal spaced then Qimage fills the page negating the effect of the trim unsed paper setting in the driver as the gaps between the images expand to fill the page.
I would like to be able to load a selection of images with borders then for example specify a 10mm gap between images+borders then print optimally spaced this would mean I could set the paper length long then the driver would handle the top and bottom white space with the remove top/bottom blank areas of the driver. Perhaps a preference setting for the optimally spaced setting this could then also include Joost's other request re sorting.
Could we therefore have an optimally spaced setting with user definable gaps and the option to retain or discard sorting for roll fed printers. I am assuming in this that other large format roll fed printers can remove top and bottom unused space from prints.
Regards
Mark