Hi guys, just adding to the luggage discussion. I looked into this a lot b4 and after getting my Eva107, and couldn't justify the Energica cost, even if it had a basic bracket system. I can see two very good mounting points (under seat x2, and under the 'hand grabs' x2), but any custom rack should really be minimal and hopefully double as a grab rail for the pillion.
For me, I figured I would just strap a bag on the tail when I ride long distance, as my wife only jumps on the back occasionally. But a set of the Givi 101B came up for around 60usd/100nzd used only 3 times, so I jumped on them to try. I'll report what they're like soon, but plan to put the strap UNDER the seat so it's not interfering with charging. The main issue I might face is the bags pointing towards the rear tyre when filled, but it's pretty easy to attach a bungy from one side to the other to pull them more together if this is happening. It's basic, but it's also cheap. I'll let you know how I get on. Failing this, I'll be looking at a rear rack that I can strap a waterproof bag to and just work with that.
E-otearoa (riding in NZ)