All right, I want to start off by saying that I have searched most of the sport bike forums and they all have some version of a method which typically involves drilling out the stock bolt hole and using a chintzy looking over-priced pin.
My method is (nearly) completely reversible should you need to. This is definitely not the only way to do this. I used 100% of my brain power and this is what I came up with. Sad, I know.
I would not recommend anybody do any
quick-release method if you intend to carry a passenger. You should only use the stock bolt when riding 2-up. The main purpose of this for me is to quickly throw on my saddle bags to haul books to school.
2 6mm x 55mm x1.0 bolts (With the smooth part on the neck) Edit: If you ride 2-up a lot, you could get a bolt that is threaded the entire length. When you are done, you have the option of using a 6mm nut on the end when you carry a passenger.
2 1-9/16 "Safety Pins" (Not sure why they are called 1-9/16, they are 1/16" thick)
You could get by with only one of each of these, however it is good to have a backup.
3/32" Drill bit
Vice or vice grips to hold bolt while drilling, or you could use a drill press.
Needle nose pliers
First, cut the head off of a 55mm bolt. I used a dremel. Screw it into the hole and slide the seat over it to see where you are going to drill the hole for the pin. Alternatively, I found a small washer that was the same thickness as the seat bracket and the bolt was easier to get to. Try to mark it so that when the bolt is all the way in the pin hole is horizontal, although this is not crucial it will help later.
Next, drill a hole in through the bolt big enough for the pin to go through. I used 3/32". To avoid having the seat be excessively wobbly, I put the hole just a touch closer than I thought it should be. You can always unscrew it 1/2 turn if you drill the hole too close. After the hole is drilled in the bolt, you can feel free to shorten it and deburr the edges. I also used some flat black touch up paint.
You should have something like this:
55mm bolt, fancy custom bolt, stock bolt. The extra bolt is in case you mess one up.
Next we need to drill a hole in the seat bracket, next to the bolt hole. Like so: (This is the only part that can't be undone)
Now we need to fashion a pin that will work for this. Grab your safety pins and get to bending. It's hard to explain how to form this pin, so I will show you with pictures:
Here is the original one on the left and the finished one on the right. You should make two, just in case you lose one later.
Now test the pin out for size. Be careful if you adjust it, because they get weaker every time you bend them. Stick the 90 degree end into the bolt first, the push the hooked end into the hole we made. To remove it, pull the hooked end out of the frame first, then it can slide out of the bolt.
It looks bigger than it is in these pictures, but I think there is room enough to make it smaller it would just be harder to take on and off. If it looks good, test the seat out and make sure that it doesn't wobble too much for your liking.
There is definitely other pin configurations that could have the same effect.
If all is well, we need to use some thread locker on the bolt (blue so its removable). Since we need the hole in the bolt to be horizontal, you probably can't tighten it down enough to keep put without thread locker.
So here is what you'll be left with:
Once it's done you can see just a bit of silver sticking through, but it is not enough to feel or notice unless your looking for it. I might put a bit of electrical tape on the contact point to preserve my paint, and once the seat flap is down you can't really see much at all.
Last thing: throw the extra pin under your seat. In case you are out and about and drop, lose or break your pin you wont be stuck.
Obviously this mod is not for everyone, but hopefully it helps a few of you out.