gcon - That top box looks like a Givi Trekker Outback, quite large.
I also have the ATAS and am looking at getting a topbox. Your mount seems to have a silver plate and that looks like it is supported by a black structure beneath it. So I assume the rack was not able to take the weight and needs bracing.
Honda don't do a top box for the ATAS, I don't know why.
The top box I am interested in is the Givi Trekker Dolomiti which is similar to yours but smaller. I have the OEM panniers for trips away so the top box would be for days out.
Could you give me some details of the mounting of your box please.
Lol @ Davy F! I don’t want panniers and this 58L Givi Trekker box was the only one that’ll take 2 x helmets so it was the best option for me.
Sorry for the delay folks - here’s the pic of the rack and plate. It’s a Givi SR1161 rack, which I had to order from Italy (but I now believe they’re available worldwide) and a Givi M8 plate. Hope this helps!