Flexing a Flex Plate?

OK, so I went hi-tech with some cardboard (Grandchildren took my PlayDoh) and made a measuring template.

Turns out there is a difference in pad heights; the new ones are slightly lower.
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The **** that turns 15 minute jobs into 4 hour ordeals....

From the above, looks like the consensus on my original thought of flexing the flex plate is "don't".

That would leave washers or a different TC as the other options.

Anyone else running with washers? Any down side to that idea?
I successfully ran a Hughes 24-20 converter with stainless steel washers between the flex plate and the converter, LA340, 452 HP, 727 trans. Swapped it out for a 24-30 no washers needed.