<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I'd think if your box was not the exact same it would be considered marking. </div></BLOCKQUOTE>
It would be considered an "unapproved container" and under KCBS rules your entry should not be accepted at the turn-in table. If time allows, you would be given an approved container and allowed to enter a legal box.
If you turn in a broken box, that could be considered "marking" and subject to disqualification based on a subjective opinion of broad authority given to the Contest Reps.