2 Pet 3:9 "The Lord is not slack concerning his promise, as some men count slackness; but is longsuffering to us-ward, not willing that any should perish, but that all should come to repentance."
1) provide proof that this verse is only references the elect. Prove that the indefinite pronoun 'any' refers to only the elect.
2) if "any" only refers to the elect then this verse refutes "eternal security"
3) "all" cannot refer to the elect for the elect have already come to repentance. No one is saved who has not repented of sins.
the doctrine of predestination goes much deeper that even your explanation. The text of II Pet 3:9 is a direct refutation of predestination. If not, then God does not really know who He predestined to salvation from the foundation of the world. Why would God actually think that any He predestined perish. It implies an outside factor than God here. That factor is man and man's faith and belief.
It clearly shows the fallacy of the reformed view of predestination. It must be held in isolation of the rest of scripture otherwise it becomes quite obvious since it never aligns with scripture.