I recently and coincidentally ran an optimization among CD's, LSBRX, and VWAHX using their total returns over the past 9 years, including doubled YTD return.

It turns out that 100% CD's gives an average return of 4.1%, standard deviation 1.7 % over the past 9 years, assuming a new term is negotiated each year (unlikely).  However, with a mix of 50% CD's, 38% VWAHX, and 12% LSBRX, the average return would be 5.3% and the standard deviation would be less...only 1.6%.  The three assets are slightly negatively correlated.  So, it seems that by adding the 4.5% tax free yield of VWAHX and the 6.5% taxable yield of LSBRX, with a chance of price appreciation, you would have a good, safe income portfolio.