I was on a short trip on the weekend and wanted to have my luggage on the bike instead of carrying it on my back. (Unfortunately, I don’t have a front bag yet.)

Some detailed shots of the attachment:

Wooden rod attached to underside of Brompton Backpack and backpack shoulder straps layed over

During my trip I realized that my legs are hitting the rod a little. I repositioned it a little further back during the tour.

Backpack attached to Brompton rear rack

To increase the stability, you can wrap the rubber straps around the rack (behind the wheel) which will increase the tension of the straps.

The idea was taken from Gianni who has a lot of great tips around Bromptons touring: https://piped.video/watch?v=vfQe4f0jbZs