Wiring up a 2 speed wiper switch with Painless

Hi Folks,

Greetings from the UK.

I have a 66 Dodge Dart I'm currently restoring. I'm currently changing the wiring to a Painless kit, and wondered if anyone could help with the specifics around the wiper switch.

I currently have it wired up as per the original loom, apart from the very bottom connection (has the silver metal swooping thing on it sorry I'm no expert) . I was hoping one of you know where this connection should go to as it definitely not to ground,and the original wiring diagram shows it running to reverse, but not sure this will work with painless.

If anyone's wired one up with a painless kit before I'd really appreciate your input.

(switch like the image attached... Image from Google and just for ref)

Thanks
Stan