Why would you want less rounds???? If you have mags that hold over 10 rds you are already in legal possession of them and there is no reason to block it. Those mag blocks aren't permanent so you wouldn't be able to sell the mags either
Now that these have been posted to MDS they will be added to the MD list of illegal items .... so that the next law banning mags holding "X" amount of rounds will not allow existing mags to stay in state.