Dell 1100MP projector display size problem

We are ceiling mounting (using Chief parts) our Dell 1100mp projector and can not get the display  to fit the smartboard correctly.  We brought in another vendors projector and no problem.  What do  we need to do?  It has been mounted 8 feet from the smartboard.  We can get it right if the projector is at seven feet above the ground, but  for security purposes this is too low.