You can add a "single desginee" URL code to make this form not only fill the radio button, but will have the fund already selected!

You do this by changing the existing links wherever they are to this:

This is what makes it work:

The 2025 being the ID for the Designee fund.

So this will work for any form, if you follow the same method, I found the tools to do so here (Regular old help file):