Condition-wise it is the same problem as your original "Weighty thoughts". You have to excuse my grammar. I meant there is a balance-type scale, where you can only weigh one side against another and see if one weighs more, or another, or they are equal. My variation of the problem explores some logical inferences that we passed in your original post.
I believe, I solved this problem. If I point out what's wrong with your proof above, it would be a dead giveaway. And I think you might enjoy finding the solution on your own.