You have - inadvertently I'm sure - penalised all those players that played by YOUR rules.
Many of them are now effectively worse off. Specifically:
1. Those that didn't bother to enter the CG as they knew they wouldn't have the time to reach the top 25%.
2. Those that entered but quit before 75% for the same reason.
If you are interested in being perceived to be fair (actually, just being fair!), and if you want to retain confidence, you should hand it out to everyone, and give the top 25% a paintjob or something, so at least their effort is rewarded.
Many of them are now effectively worse off. Specifically:
1. Those that didn't bother to enter the CG as they knew they wouldn't have the time to reach the top 25%.
2. Those that entered but quit before 75% for the same reason.
If you are interested in being perceived to be fair (actually, just being fair!), and if you want to retain confidence, you should hand it out to everyone, and give the top 25% a paintjob or something, so at least their effort is rewarded.