The Dirt Shack

Started posting this over in the Non-traditional Designs forum http://www.tnttt.com/viewtopic.php?f=5&t=58309 but after reading more I have decided to make it out of foam and am calling it The Dirt Shack.
I am starting with a utility trailer I already own and still trying to figure out how I want to seal the part below the pre-existing rail:

Went from a very basic design without curves:

To this(I can't take credit for the dirtbike, I found it online):

Thinking of using removable slats for the floor similar to how modern bed frames are made. This would allow me to fit 2 full-size dirtbikes in the trailer while in haul mode and once the bikes are unloaded the slats could go back in to support a futon mattress or regular mattress if I go that route.
I am also planning on making the platform completely removable from the trailer. Thoughts or advice?
I am starting with a utility trailer I already own and still trying to figure out how I want to seal the part below the pre-existing rail:
Went from a very basic design without curves:
To this(I can't take credit for the dirtbike, I found it online):
Thinking of using removable slats for the floor similar to how modern bed frames are made. This would allow me to fit 2 full-size dirtbikes in the trailer while in haul mode and once the bikes are unloaded the slats could go back in to support a futon mattress or regular mattress if I go that route.
I am also planning on making the platform completely removable from the trailer. Thoughts or advice?