Flexplate is not fits the torque converter

Notice in that previous picture you marked up the flex plate is sitting with “ENGINE SIDE” down.
The middle area you marked on a 10242 is about 0.325” larger than a 10136.
The top area at the point of the notch on the 10242 is also about 0.325” larger than a 10236.
The bottom area at the point of the notch on the 10242 is about 0.285” larger than a 10136.
This means there is a gradual taper from the middle to the bottom. Not sure if that is intentional by design or just from manufacturer tolerance.

Now, the 10142 is about 0.112” thick. The 10236 is about 0.130” thick. Not sure if that makes a difference in the weight offset, but I doubt it because the weight removed is also thicker.