At first, since you have changed the table, I think that you have knowledge about PHP and table of Q2A. You need to observe qa_db_upgrade_tables() of qa-include/qa-db-install.php. Q2A updates only portion required for upgrade without refreshing no tables. The process of update will changes by the changes of your table. When your change and change of Q2A have collided, it may be necessary to apply your change again after update. However, probably, in many cases, it will be unnecessary. Anyhow, it is important to fully investigate program.