Although I questioned the size in the OP, I eventually also bought one of these same bags. I too have the EVO model, which uses a bike specific tank ring to latch the bag onto. I now have tank rings on all three of my bikes (FJR, Vstrom and VFR) and the tank bag snaps onto whichever of the three I opt to ride any particular day, which is very convenient.
I have one of those three port cigarette lighter 12V power point inside the bag, which I have powered by an SAE (Battery tender) type cable. Since all three of the bikes have battery tender pigtail cables on them, I can power the tank bag on all three bikes also. The power in the bag goes off to the Starcom1 intercom I have in the mesh pocket under the bag's lid, the radar detector that I have velcro mounted on the top of the bag's lid, and a quick disconnect cable that runs to the zumo GPS I have mounted on the left side bar. So all of those functions move from bike to bike with the bag.
In terms of size, I'd never had any interference issues on any of the three bikes, until I put the HeliBar riser plate on my 3rd Gen. Now the bars will just touch the sides of the bag at full steering lock, which really doesn't bother much except it turn the cruise control power button on or off on contact. The horn button and other switches do not seem to hit the bag.
One recommendation for you if you do decide to get one of these: On the small back pocket of the bag is one of those slit-able rubber cable ports in case you want to pull wires through from inside. I recommend undercutting the stitching between the rubber flap and the bag and removing that rubber piece, as it will make a big ugly black rubber smudge on the belly area of any light colored jackets. If you wear black all the time it is no problem, but my nice new bright HiViz Olympia AST2 has permanently been branded by that rubber thing. And no... my belly is not all that big, at least not on the FJR aged rider scale.
One more thing... while the bag is supported above the tank on the tank ring, the extended rear of bag does touch the tank in the back. You'll want some sort of paint protection at that contact point, either some sort of clear membrane, or any type of typical tank / zipper protector. I have the TechSpec snakeskin tank protector and just have it positioned high enough so the rear of the bag sits on that.
(I've since moved my GPS to the left handlebar to get it up higher in my sight line)