yes, it is possible.
i've done this with my mimaki jv3, but i'd imagine any printer operates the same way.
the theory is, that, when you load material the printer scans the page width and this is the basis from which it prints.
therefore, all you have to do is "trick your printer" into thinking the media is wider than it actually is:
-you'll want to apply low-tack vinyl strips to the platen (or masking tape, must be white'ish... i've used post-it notes) undereath and just outside the print material to the width of the default margins of your print. takes some trial/error but you can dial it in.
-the printer then scans the media, and includes your strips into the overall width of the page that can be printed.
-you should be able to remove the strips after the initial setup/scan, but leaving the strips on during the print also allows to catch the ink that may wind-up on your platen, should the material drift during print.