Federal Reserve notes are stock certificates. There are enough of these generated in various denominations so that they are easily traded - currency. Motla68 found a great link -
Title 12 U.S.C. §411 et seq. You as a bank have to buy FRNs, for them to be issued to you. Since 1933 to save the Fed FDR opened this up to everybody as quasi-Fed banks. You buy the FRNs with your labor, your salary checks.
You buy stock in the Fed when you cash your paycheck by endorsing private credit.
You choose not to buy stock in the Fed when you cash your paycheck demanding to redeem lawful money.
If you go with Pete HENDRICKSON's Cracking the Code technique of a Zero Income Return you argue no liability on worn out interpretations of Title 26 (IR Code) after you have already bought Fed stock. If you demand lawful money at the initial transaction, cashing your paycheck therefore, you have refused to do business with the Fed. Now you are just using that note format because it is the only recognized currency and therefore lawful money. It is fully bonded by the obligations of the United States for creating the Fed.
In this description of the contracting I do not see how one can interpret resorting to the Demand provided by law making you an agent of the Fed. You are demanding not to be in agreement with the Fed. If anything you are making the declaration that Congress is your agent, making you the sovereign. That is to say your agent provided the remedy written into the law for you to remain the sovereign.