Another method that works just fine is to hold them by the carapace gripping in the area immeadiately anterior to the connection of the plastron to the carapace. The leverage is good and you are out of danger. The added benefit is that they can't dislodge your fingers like they can when gripping behind the head.
The method that I choose is usually dependant on the position they are in relative to me.
Note: the behind the head hold also works with commons, the side grip doesn't as you are in range.