To collapse the left or right block columns in any module you simply edit the call to the printpage function. For example in the reviews module (function reviews_show) you would find:
$mklib->printpage("1", "1", "{$mklib->lang['re_pagetitle']}", $blocks);
The first "1" is the left column and the second "1" is the right column. To collapse the right column you would change the "1" (open) to "0" (closed) like this...
$mklib->printpage("1", "0", "{$mklib->lang['re_pagetitle']}", $blocks);
Just search the module index.php files for "printpage" and you will be able to find all the places where this code occurs. It is basically the same for all modules. You can collapse the columns only for the particular screens that stretch the portal or you can collapse them all.