Thanks SS - there is space to the outer edge, In-between, and front of water bottles. That's where I've stored stuff like tools, tubes, etc, that I don't need constant access to.
If you look at the box from a side view, you will notice bottles are angled. The back portion of the bottles are about 1/8" from bottom of box, with the front portion being a few inches.
The box is molded to the Thor seat sport g model. The other seats I have are Hostel Shoppe, I'm sure I could figure something out if I really wanted to mate the other seats the box.
Something I forgot to mention - the water bottles and box lid are supported by the seat and not the box. I stole a bunch of ideas from: Jim Parker, Ratz, Jason, and Gary, and Bentup Reumbents.