How does the "Curve" affect Kellogg's 3-D grading?

I have a bunch of Kellogg's cards from 1970-1977 and was going to pull a few to send in to have slabbed in my next submission. I have never sent any in so I'm not sure how they go about grading them. I know if the front, 3-d area has cracks, etc, it drastically lowers the grade but I wasn't sure how the curving affects it??? Some are pretty flat and I don't have to worry about it but others are curved upwards and I am putting them in sleeves and card savers then under something heavy to try to flatten them out. Any experience from board experts??
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It doesn’t effect the grade. The same can be said for Topps cards that have a “curl” that were removed from mid-late 80’s factory sets. As long as all other attributes of the card were good, I’ve pulled gem 10’s on cards with a “curl” straight from factory packaging.
Edited to say that with Kellogg’s cards, I have seen some cards “crack” in the slab post-slabbing due to this curl. I haven’t seen it in some time, but it has happened.
Thanks for the input. I have indeed heard the stories of them cracking after being slabbed as well. I don't think I have many that I'll be sending in besides some stars from the early 70's and I did find and interesting one.... 1977 Ron Cey that is the "58 HR" variety. No clue what it's worth but there are only 2 on the pop report so figure for $7 I can't go wrong.