find the file
includes/templates/theme399/css/stylesheet_main.css
there is a line of code
.main-indent{ background:#171717; padding:26px 10px 4px 26px;}
replace it with this
.main-indent{ background:#171717; padding:26px 0px 4px 26px;}
this will take away the right padding
Please back up that file before editing
and since i did not fully review the template
it may be necessary to revert it for proper rendering later on or in a page that uses that class (.main-indent)
I don't think that it might cause a problem, but better safe then sorry
hope it helps :)