The better solution would be to have an @media profile in the CSS if the screen does not reach a certain width, thus calling a "display:none;" on the L/R columns.
To take things a step further, another action that could be written to have the forum software use "post_top.tpl" code rather than "post_side.tpl" code if the browser does not meet a certain width. Both files should be combined to one and have each section used based on screen width. Responsive website design.
This is all part of adding responsive design to UBBT and not difficult for the UBBT software writers to implement.