I would think there is a need for better Club recognition, such as clubs required to provide yearly rosters of paid members, up to date by-laws. The way it stands now a club could pay for 3-4 members, even though there are more than that in the club. I would think that the Broker & the Carrier would want a more accurate count other than one done on the honor system. The real test will be when the first claim is filed.
The policy provides for an audit for the premium. At the end of the audit, the club will be billed for additional premium or refunded excess premium. I wouldn't be surprised if there is a "mini-audit" annually around about the start of the next coverage period.
From a budgeting standpoint, it would make sense to make a good faith estimate of what your membership is so you don't get hit with a big bill after an audit.
You would want to keep good records of membership as a lawsuit can happen several years after the triggering incident to make sure that you can prove that club members involved in the incident were in the club so that there is the possibility of insurance coverage.