your contributions are limited but i-bonds, through treasury direct? guranteed not to lose principle and you get an inflation adjustment. Maybe a 2% yield with no principle risk? You have to at least leave them in for 1 year before you can withdrawl. I am spreading out my contributions so some money will be available every month.

I would not mind a floating NAV on money markets EXCEPT .... than any mm transaction in a non-retirement account becomes a taxable transaction what a pain in the petuty. I have been watching MINT too waiting for a price pull back but it is not happening. if you divide yield by price volatility, BSV is about the same as MINT. I have a brokerage account at vanguard so they let me trade BSV for free. BSV is 80% treasury, 20% corp. 3 yr duration.