How about trying using the replacement line:
$blockshtml = $OUTPUT->blocks('side-post').$OUTPUT->blocks('side-pre');in Boost's 'layout/columns2.php' file until you're able to change all of the block positions to 'side-pre' somehow. Please test on a test server first though! If this works, then create a child theme of Boost and use that instead of Boost so that you'll be able to update easily.