I just went through some first time borderless printing issues on a 9800. Here is what I learned
Borderless printing only works with certain roll widths. For example it works with 44" rolls but not 42". To get it to print on the 42" roll I bought especially for this purpose I added an extra 2" on to the edge by carefully, flatly, extending the bottom couple inches of the roll by taping a letter size sheet to the backside. BUT I also disabled the paper monitoring in the printer panel, and I think that may have been enough. All of this is to get the printer to print the entire WIDTH of the roll, so your left and right edges have no white, assuming your image is the same width or bigger than the roll.
To get the printer to trim the TOP and BOTTOM you need to enable borderless printing and then "double cut." You can either have the print driver enlarge the print for you or enlarge it yourself. I am writing all this from memory, if you still get stuck LMK and I will go to my workstation and get the exact workflow.