The PM limit is going to be raised as you increase in rank. Your copper membership won't lift these limits.
You posted the correct links but you confused the OP with your above statement.
1. PM limits are governed by "Activity" not by "rank".
2. Copper Membership automatically whitelist the user, so OP should have increased PM limits.
OP, if you are not getting the privilege that are mentioned
here then you should PM
theymos or can create topic in
Meta about your issue.