Running Hand2Note4 together with many Google Chrome tabs dramatically slows down your PC. Limit Chrome to 2 tabs during play, or switch to a different browser for sessions.
Lower the number of threads used in the program settings.
Decrease them gradually. After each change, rebuild your stats and test the program’s performance.
If the speed is acceptable — keep the current setting.
If it still feels slow — reduce the max thread number again and rebuild the stats.
Based on our subjective testing, these configurations showed the best performance:

Remove unnecessary stats via Configuration > Delete Unused Stats (make sure to archive your
Config folder beforehand). After doing this, you will need to rebuild your stats.
