FG suffers from a pretty severe degradation in R value in mobile applications (it takes longer but still is an issue in stationary applications, too). Foam would be much, much better in three ways: Sealing, structure, and consistency over the life of the house.

I'll have to look back into the foam. To be fair though this trailer will likely never move. I'm doing a bit of statist jujitsu. It cost a fortune in fees and permits to build a house but I don't need a permit to build a trailer. And my specific county will allow tiny houses as the primary residence. So it is an inexpensive temporary solution. The long term housing is to be a barndominium but I'm trying to get all my debt paid off before that. Then the tiny house will turn into an airbnb or a hipcamp situation.