To create linear movement the force of the bed must move vertically through the centre of mass.
The pupils body shape may change during the flight phase, but no additional rotation can be created whilst in the air.
If the force does not go exactly through the centre of mass it will result in travel away from the cross. The direction of the travel will depend on the direction of the force and the position in which it passes through the centre of mass.
No rotation should occur during linear momentum (straight jumping on the spot).