I figured it would be obvious enough from what I outlined that the yes/no answers from the tails results gives you a proportion of "yes" answers, such as, say,

I figured it would be obvious enough from what I outlined that the yes/no answers from the tails results gives you a proportion of "yes" answers, such as, say, 20/50, which is the proportion you want. The doubling is just 20/50 = 20*2/100. But I can appreciate that maybe someone else doesn't quite see it! :)