Pictures of chassis at datum points "E" and "F", plus dimensions:
Datum point "E" left hand internal views; view from the front of frame member (left) and view from the rear of the frame member (right).
Frame height is 18 cm at this point. Note the frame reinforcement (inner frame rail) in the left hand picture:
Datum point "F" at the rear frame cross member.
Frame height is 14,5 cm at this point.
H.