We run our surveys on Backerkit the largest crowdfunding survey company!
You have two options:
1.) Add extra money now, which will count to stretch goals.
2.) Purchase the add-ons via Backerkit, our project management software.
We are running our project on Backerkit so you will receive a survey after the campaign to either spend the extra money you added or purchase the add-ons on Backerkit.
Don't see the answer to your question? Ask the project creator directly.