[Dave Keenan:]
>This is optimally tuned in 12-tET with 13.7c errors all round.
One third of an octave minus the fifth harmonic (or the difference between
their inversions) is also the same combined 'error'/difference of 19:24:30
(or as an 'inversion' @ 19/15 & 19/12) from 12-tET.
Dan