  We present two improvements to our previous dynamical overlap HMC algorithm.
We introduce a new method of differentiating the eigenvectors of the Kernel
operator, which removes an instability in the fermionic force. Secondly, by
simulating part of the fermion determinant exactly, without pseudo-fermions, we
are able to increase the rate of topological tunnelling by a factor of more
than ten, reducing the auto-correlation.
