mack daddy
Brian H is correct, hanging more wire on the loop changes the frequency. You could try a passive have wave antenna by placing a 18 inch copper wire next to the MS12A, near the corner where the loop is positioned. I have tried this before, Palm Pads and Stick-A-Switch but with mixed results.
Making the receiver more sensitive as a better solution if you can do it. (Simplest is to add more wire to existing antennas for CM15, RR501, TM751).