If you'd like to carry your custom URL parameters from the landing page to the thank you page, just include the parameter "carryParamsForward" in the URL. This will ensure all the parameters from the landing page will carry forward to the thank you page.
For example, if your landing page is: https://raisedonors.com/test-org/campaign-name?fname=Chad&lname=tester&utm_source=source-code
You can carry the same parameters through to the thank you page with this modification: https://raisedonors.com/test-org/campaign-name?fname=Chad&lname=tester&utm_source=source-code&carryParamsForward=true