This is only a guess, the 2 positions just below the left pop bumper. On El Dorado the two 1 3/16th inch posts are listed on the play board. But not numbered in the diagram. The only other possible location is under the white plastic ball guide that's on the right side.

For Solar City and Target Alpha the 34 posts are all the same, 1 inch. Hopefully some one with the correct answer will chime in.

On El Dorado they are positioned adjacent to the stand up target in front of the lower pop bumper with the small plastic on top.