Revert back to positive inflow (+sig_nn) for reason:

1) Fully symmetric system ala:
  |A   B^T| |x| = |f|
  |B       0| |y|    |g|
2) Still have positive-definite system when stabilized in almost anti-sym formulation because:
  => d + f1 + f2 + h > 0 (quadratic term)