  We use a space-time asymmetric O(a) improved fermion action and fix the
asymmetry non-perturbatively to restore the relativistic dispersion relation.
We compute spectra and matrix elements of quarkonia and heavy-light mesons and
compare with results obtained using a symmetric action with the Fermilab
interpretation i.e. that the physics of heavy lattice quarks depends solely on
their kinetic mass. We provide additional evidence to support this.
