What values are you using for source and template smoothing? You
may want to increase or decrease it a little. I've used values between
1 and 1.5mm and have been typically safe from over fitting effects. Depending on resolution, you may be successful at smaller values.
In my case, I have not smoothed the source or template.
Your number of nonlinear iterations is much larger than what
I've been successful with. You may want to start with
0 nonlinear iterations (ie linear only), and try runs adding more
Ok let me try.