I like it.. Can’t wait to see how you get to the end of this project..
Nice work - I’m going to be attempting a similar build on my 2005 ES so this is great documentation to have!
I’m guessing you will include a platform of sorts for feet and some sort of rear bumper? Angle a foot rest or peg/bar to press your foot against to keep from sliding off the back. Maybe even a grab handle at the base of the seat.
Might also consider incorporating a set of lights somewhere since two adults will block the existing lights.
Bonus points for a little folding mini bimini (might be fun).
That looks awesome, 
I wish I could weld, one bump and the whole back end would fall apart! 
Its an 02. With stock front brakes and a full weight load you can use the bimini as a drag 'chute
Is a new thread really necessary for every step of the project?
Oh yeah, congratulations.
Must be Groundhog Day, every day is a repeat.