Getting a long Gravity Form to scroll in a pop up

I've a long Gravity Form displayed in a popup. I've applied some CSS to it, and I want to use the Minimal style instead of the Simple style, but I just cannot figure out the right CSS element and rule to apply to get it to scroll. It does scroll in Simple, but not in Minimal or Cabriolet, but I can't figure out why that is the case. The form just gets cutoff. I'm thinking the solution is overflow: scroll, but I just cannot find the right element within the popup to apply it to.

Could you guys take a look and see if you can figure it out? You'll have to be logged in to see it and I've enable support access. The form will get displayed in the popup here

Also, is there a way to change the "Never see this message again" text on just this one form?