I'll add a second endorsement for "no" to active management in the bond funds. There's not enough margin in regular US government or corporate debt to justify paying active management.
Distressed debt and foriegn debt? Yes, but the best folks in that space have their own closed-end investment shops and aren't.
As for the potential for loss? Yes and no. If you buy an individual zero coupon treasury today that is due in 2049, it costs around $53 to be guaranteed a return of $100 in 2049. The $53 is based on the market interest rate and time to maturity. It price will change, but it will eventually still climb to $100 by 2049. Not a bad deal since some other developed countries have a near zero percent yield. I see more upside in those than downside if worldwide rates continue on their trend.
If they don't, then my 60%+ stock allocation offsets the low performance in my bond side and I'm still retired early