While I agree that shade is a cover crop benefit, a living cover crop competes for moisture and nutrients, even if it may being supplying some(nutrients) in return.

Your experiment reminds me of my many experiences with young engineers. Assigned to a line or operation, they want to change things to what has been tried in the past. It can be explained to them that the reason it is not done now is because it failed then. But there is the same confidence, enthusiasm and "someone missed something and I know what it is" attitude that encourages history to repeat itself. 

I, too, am interested in experimentation, and I - against the cautions of others, and with all the confidence...etc - proceded with my fall cover crop plan.

Well, I think you know the rest of the story. 

Of all people, I should have known.