Thats correct. The pocket in the lower a-arm is not big enough for the bag not to rub if just set in the lower arm. Bolt the cup to the bottom of the bag so that the bag is raised up out of the spring pocket in the lower arm.
I will see if I can find a picture.
Look at post #44 in this thread. It shows the cup sitting in the lower arm.
http://67-72chevytrucks.com/vboard/s...=377272&page=2
Also in the same thread, post #96 photo's 4 & 5 show the bag assy with the brackets and plates from suicide doors.
hope this helps...