In this case the from height is 5 ft: the pressure at the bottom of the form is 750 pounds per square foot.
So 12 inches up the pressure on the diamond would be approximately 600 pounds per cubic foot.
Dividing this by 144 to find pressure per cubic inch (600/144) 4.166 pounds.
(the diamond is 3.75 x 3.75). The pressure at the bottom diamond approx (4.166 x 16) 66.65 pounds.
The pressure at the top diamond is approx 16 pounds.