You don't need 16 banks to eliminate all risk. You need one bank and a treasurydirect account.

Anybody, including corporations and partnerships, can safely park excess cash at treasurydirect.gov. Buy short term treasuries and time the redemptions to coincide with next month's payrolls. The shortest bills are 4 weeks and they're paying like 4% right now.

I honestly don't understand why more people don't do it.