Good news! You don't!.
Keep your current early bird pledge and just add extra $9 for each extra pin you want! <3
This also applies in case you want more than 10 pins. Select the 10-pin pledge, add $9 for each extra!
If you have a non-early bird tier under 10 pins and decide that you want more, you can always switch your reward to another with a higher amount of pins, as long as the project is active!.
No need for add-ons! (unless you want more than 10 pins)