Right first of all make 2 new layers.. one for one stunt and one for another.
Next press this:
[img]http://static.filefront.com/images/personal/t/T3RM1N8R3/41528/kddomiuqyh.jpg\" border=\"0\" alt=\"IPB Image\" /]
It is called trackmotion, just resise the videos into a splits screen and bob's your uncle you've got a split screen.