Decided to update this thread. This configuration has worked well for us for the last six years. Kids have got a little bigger, and my 15 yr old hitting his head on the cage while sitting in the rear seat has become a problem. After getting a wider rear axle (60.5") I decided I could add about 9" of width to my rear seat by narrowing my inner fenders. I cut out 4.5" from each fender, and filled in the floor. This gave me 45" of room for a wider rear seat. I found a fold and tumble seat, and narrowed it about 4" to a width of 44", then had it covered to match the front seats, and moved it back to the original location (which is 10" further back than stock because of the stretch). Kids now have plenty of leg room, they can fit 3 across, and I got my rear storage area back. They are also sitting forward enough where they don't hit their heads on the rear of the cage.
I added 1" wheel spacers to make sure tires don't rub in the inner fender, and I verified that it doesn't rub on the trail. With the spacers, I have 3 1/2" on each side between the inside of the tire and fender. Without the spacers, I am legal with fender flare coverage.... I also removed some tubing that I had the rear seats resting on, and mounted the new seat back to the floor. I reinforced the bracing under the floor a little also.
I will bed-line it again, and cover up all my ugly welds. I also connected the rear of the cage to the frame.