I believe you can't ever have enough rear visability. I don't understand why Yamaha would make the front blinker illuminate but skip the back...but they did. FOund a neat little kit from a company called Electrical Connection that coverts our rear blinkers into running and brake lights by using a LED string.
Rear Turn Signal Conversion Kit
Kit was about 65.00 shipped and came in 5 days. Instructions included were very vague (IMO) but the web site showed some detail instructions with pictures for our Liners - but instructiojn sort of stop short of completing the install leaving the installer to figure it out themselves. Kit too about 2 hrs to install. You have to remove the rear brake light, turn signals, and stems. Hardest part of the install was getting the LED strip positioned right in the turn signal lenses. Wiring was pretty straight forward with color codes provided. Wires to the Led were small and hard to work with. Company provided Scotlock type connections (which I despise). I chose to solder and shrink wrap after the first time I hooked everything up, bolted it back together and it quit working because a connection pulled loose. You will not be able to use the factory signal stem (internal) waterproof plugs (must be cut off) because there is not enought room for the 3rd LED wire. Instructions don't tell you that.
Once working the setup is pretty cool..the Led rings match the brake light intensity for running and braking. They stop illuminating when signalling.
My first impresson after the install was " I wouldn't recommend these to anyone", but now that I'm done, had a beer, and they are working, they provide a lot more visiblity to the rear of the bike and work really good. I'd give them a 7 of 10 simply because of difficulty of installation and cheesy connectors.
One note: If you buy this kit, make sure you wrap a towel between the brake light assembly and fender to keep from scratching your paint - working area is tight because the wires are all still connected.
Any questions, shoot me a PM.