That is a GREAT idea! I generally don't lock my helmet and every time I've wanted/really should have - I was too lazy to pull it out of the "glove box" under the right side cover. I still need to lube those grommets up with some silicone spray. Only had this bike for a a month, just hit 1,000 miles - love it!
I set my helmet on the seat and strap it around the back rest bar at the very least to it is attached.
I will not use their helmet lock as i do not want my helmet on the paint. I can secure both my wife and my helmets by setting them on the mirrors and running this cable through the D-rings and handle bars . it also fits inside the gas cap door along with my registration that is inside a baggy and stuffed into the crack. I also have the inside of that area covered in that rubber material with holes everywhere to protect the paint and no rattles. Very happy with this set up
I agree that side cover is a pain. And the design for the factory lock does leave the helmet dangling on the paint and really close to a hot exhaust. For now it works in a pinch. I'll have to invest in a cable lock eventually.
That gas door isn't huge but will fit a few things in a pinch. I even stuck my sena 30K unit in there after detaching from the helmet.
On a bike this big it would have been nice to have a waterproof lockable compartment that is easily accessible. The under seat storage is a pain to get to and water gets in. but storage is storage and its better than nothing. I just put everything in zip lock baggies.