This seems to miss the point. If you are pursuing a particular rate of return, you can be almost guaranteed of not reaching it with bonds and traditional equities. Risk adjusted return is only one framework for examining your portfolio.
You can simply lever bonds, equities or most other investments by a variety of means. For example you can get way more risk in 2-year US gov securities via futures than would be sensible.
Likewise, you can de-risk an asset by holding cash alongside that asset.
You can redistribute the same amount of money into the other (better) half.
Reminds me of the old advertising saying about knowing half the advertising they do is useless, but they have no idea which half.