I use Kappa bag with Givi shoe. (Kappa is low-cost Givi). There is a horseshoe made by Givi. It's bolted arround tank filler cap and it stays there all the time. The bag has support on the bottom and you simply click it into the horseshoe. It doesn't interfere with anything nor it touches the tank. You remove the bag simply by pressing release button.
So, Givi horseshoe is needed and from there you go on and choose either Givi or Kappa bag, the size you like, that is compatible with this mechanism.
So, Givi horseshoe you need is Givi BF18 (for our bikes) and then, if you choose Givi bag, there is XS306, XS308, XS308, those are semi-rigid bags, and then 3D603 and 3D604, those are rigid ones. I've chosen Kappa bag just because it was cheaper and it looked the same as Givi.
That is the one on the photo. It's empty on the photo. It also has expandable floor so you can gain 2-3 inches in hight if you open it.
I've ridden with it fully loaded and extended on higher speeds for long time and it has never moved.