The elevons on the Vulcan have a very limited downwards travel in comparison to the upwards travel. This can be felt through the control column once in the air, and can also be seen by exercising the control surfaces when on the ground. 

The negative G limitation of the aircraft is 0, and therefore, pushing the nose down should be avoided. The correct technique is to reduce thrust and let the nose drop, or roll the aircraft and let the nose drop.