Thanks everyone….I’m learning more as I research this….not as much info out there as there is hot dog cart stuff. I’ve learned that one of the biggest makers of the freezer box unit doesn’t even cover the inner foam….so I don’t think I need to do the metal covering. Apparantly the foam is closed cell foam or something so I just saved myself a bunch of work and $!
The more I think about this the more I think the cheaper adult trike (astrodogs idea) option is the cheapest way to get in on it and see how it might work. I can easily build a box now knowing all I need is a plywood box and the foam. If it’s successful I could spring for the icycle tricycle next year….