I am trying to figure out why my 91' cbr600f2 has a large open space under the seat. Was there a trunk there before? Was there ever anything there besides empty space?

I think I am going to make a custom box (proally sheet metal)to bolt up/weld to the frame, to create an underseat trunk, for extra set of lenses, lunch for work, wallet, etc.
The only doubt I have right now is figuring out how to change the seat so it can open and close without a rachet set. On my bike the seat is securely bolted to the frame with 2 bolts one on each side in the back and has the rubber mount in the front attached to the tank.

Has anyone done this before?
Does anyone have a bike in which the seat opens up? that has pictures of how it works?
Or does anyone have any ideas on how to make my seat a "quick disconnect"?

 

[&:] http://www.1tail.com/sa/p/TARGA_TRUN...00F3_97-98.htm