How do you submit Kelloggs cards to PSA?

I recently acquired a run from 1970-1979 complete and near complete baseball sets from Kelloggs. I'm not sure how you could package them to send them in to PSA because they have that natural curl to them which causes them to crack if you try to flatten them to hard. Has anyone done this before?
Collecting Tony Conigliaro
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Comments
You may want to try and un curl them first.
Try adding a little weighta little at a time.
Or, go to the registry and email someone who has sets listed like King Kellogg.
I don't think PSA will touch em if they are curled, but you could call Customer service and find out.
Steve
I sent in some that were straight from sealed sets and only had a slight curve when I put them in CS1's. By the time PSA got them, a few were cracked.