[Kevin]

If the problem is pervasive, you could consider suspending all social (or other types) functions until everyone is either paid in full or on a payment plan. Post the list of names somewhere all can see, encourage brothers to help out individuals who are having financial issues (e.g., find them a job). Those who are paying should resent those who are not because those who are not paying are having a free lunch on their brothers' dime.

The chapter I advise always aspires to have a 30/90 day policy in that you are suspended at 30 days past due and expelled at 90. That hasn't always worked out, but for the most part, it has, and expulsions don't really happen because everyone pays.