Importantly, the automatic notification of cash withdrawal is now just $2,500, so if you want to store up some mattress money, you have to do it slowly, lest the authorities just seize your cash. Which they will do, and have done, a lot.
If you do it carefully, they’ll jail you for ‘structuring’. And if you lie about what you did with it, they’ll get you for that. Better to let the bank report, just hide well it and refuse to answer when they come for you.