3
Many of the newer themes have additional columns. Several releases ago the XOOPS core was expanded to allow for 3 additional columns. The columns (bottom_left, bottom_center, bottom_right - although the naming nomenclature changed a little) can be physically located anywhere in your theme - so yes, you can use one of these to create your far right column.
Just look at a recent theme and you should be able to see how to add these to your theme. Then you can manage block placement using the standard XOOPS block administration interface.