Are you using the PS/Canon plug-in to access the Canon printer? If not, get this. Then what I would do is create a blank image that is 36" wide by a few inches higher on the top and bottom of your image for a margin. Let's say for your 16"x20" you would create a blank canvas of 36" x 24", giving yourself a 2" margin. Make sure you pay attention to the DPI and bit settings, etc. when creating the blank canvas in PS. Now open your picture(s) file(s) in another window(s) in PS. Then copy and paste the picture(s) into the 36" x 24" canvas. You will see that you have room for more images due to the 36" width. Not wanting to waste canvas you should consider other images you want to print. Copy and paste as many as you can and arrange each of them with a decent boarder so you can properly cut them out once printed. When you have everything arranged, drop all layers. Now you have a file of images that is fixed to print properly. The 8300 will print exactly what you see. Next you need to set up your Canon plug in to accommodate your print media. You should choose 36" and "full bleed" or "no boarders" so that the printer will print the file using the full 36" wide canvas. The drop downs are quite simple to follow in setting up in the Canon plug in. Also, make sure to down load the paper or canvas profile of your printing medium. Whoever you purchased the 8300 should have these already. Once you load these into the Canon plug in you will have the exact paper/canvas type to choose. I use DTG in Tampa from whom I purchased my 8300 ($2,325 brand new including discounts and rebates!!). The shop from where you purchased the 8300 can walk you through all of the above but what I have given you will easily solve your problem. Hope this helps.