Ok, so I couldn't ignore this! I don't know what that means about my personality but....
Yes, I have called and added people to my plans to equal 11. Sometimes it's easy and sometimes it isn't. It really depends on the popularity of the restaurant. Call and see what happens. If you can't get them added right away, see if there are any ADRs at the same place with a similar time that will fit your group or make another one for the number of people who aren't included in your first reservation. Or keep looking and see if something changes closer to your ADR date.