The 104 ft boom seems rather short for 4 elements. This would be like 26 ft on 20 meters. I have heard of 3 element 20 meter beams on 26 ft booms. Also, if you were going to insist on 4 physical elements, why not drive the inner two as a log cell and get more bandwidth? (Like the 4 element KLM 40 meter Yagi). Rick N6RK