Not had any cracking with any I flattened. There have been other problems I've encountered with Topps Chrome, such as the colors fading making the player look like the undead, or other mild splotches in the gloss due to sticking to other cards. I'll get to that some other time.
Any thicker cards I have obtained have not had the bowing problem. If I ever do get some that are, I won't hesitate to flatten them the same way I have before, perhaps a bit more gradual now after hearing that.
I might not have enough of said examples to have made an educated answer to the question at hand, I apologize for my ignorance.
"I believe there ought to be a constitutional amendment outlawing Astroturf and the designated hitter." - Crash Davis