31 and 19: meantone, generator a fifth (rms 696.65)
31 and 2*19: semififths, generator 1/2 fifth (rms 696.71)
31 and 3*19: supermajor seconds, generator 1/3 fifth (rms 696.37)
31 and 4*19: squares, generator 1/4 of a 6 (rms 696.16 for fifth)
31 does fine for any of these.