Having previously owned an ICE trike which has an attachment to fit a handlebar bag alongside the rider, I was very keen to fit one to my Kett. I missed the convenience of being able to take your valuables with you when stopping without having to lug a pannier about.
The picture shows an extension to the seat tubes with Arkel's largest handlebar bag attached. This can take my iPad Air as well as a lot of other good stuff. Also attached to the extension is a small headrest, behind which sits a small tube (just visible in the photo) that takes my sunshade!
As you can probably tell the extension is made from copper plumbing pipe, inside of which are various smaller tubes for strength, and a few centimetres of pipe that fit down into the seat. The extension can be removed by simply undoing the black strap and pulling it out so that the trike can be stood upright.
So far it all seems to be working well and although I don't have the ability to read maps or access pockets without getting off the trike, it has made touring that much easier.
Comments and other ideas welcome.