I don't think there is anywhere near enough room... check it out for yourself... the seat is extremely easy to remove.... Just pull up really hard on the front part of the seat cushion and it pop up... I think there are three connection points..
When I was working on mine we started going crazy trying to pull the back rest out, but then we found out you could just pop the seat out.
what storage area??? the plastic tray under the seat? Or the one where the spare tire is?
If you are talking about the spare area, here is an install I just had done on mine. I lost the spare and storage trays, but beyond that still have all my storage http://www.scionlife.com/forums/viewtopic.php?t=186987