q = 0.15: S_2/S_3 = 0.96058, S_4/S_3 = 0.98150
sign +1: worst relative margin -0.00003 at a1 = 0.5738, a2 = 0.5738
    margin -0.00003  a1 = 0.5738  a2 = 0.5738
sign -1: worst relative margin +0.01128 at a1 = 0.1000, a2 = 0.0200
