You should be able to determine this using modeling. You can download a very good free simulator from linear technologies ltspice.linear.com/software/LTspiceIV.exe
We have a model that simulates the PWM output of our controller at roboteq.com/files/apnotes/MOSFETout-simul.zip.
You would need to replace the motor model with a model of your peltier cell.
There are a few write-ups on the net about modeling peltier cells but these are quite complex. If you know approximately how such a cell behaves, you may be able to approximate it with simple elements.
Then, running the simulation you can see the current shape for various inductor values.