Here are two photos of stacked risers.
Here, the center of gravity of the second riser is not on top of the riser in the goal.
And in this second photo, the center hole on the second riser is on top of the scored bottom riser. Pulling out the riser to the left would shift the stack varying amounts making it an unreliable test.
What would be the guidelines for scoring when a riser is on top of two others? Which of these examples count?