Different ways to Insulate the Floor?

I'm not even sure I'm going to insulate my floor. Heat is my concern, not cold. And we won't be spending much time in the trailer before the sun goes down... We're going to try it without, for now.
But if a guy was going to insulate a cargo trailer floor, how are others doing it?
Between the plywood and the finished flooring isn't an option at this point.
Expanding spray foam seems like it would work well. I've seen attics done that way.
...Might be costly. Are there DIY kits available?
Glued, screwed, and/or taped foam board?
It would have to be attached well enough so that it wouldn't blow off going down the highway.
What are your thoughts? What have you done?
Thanks
But if a guy was going to insulate a cargo trailer floor, how are others doing it?
Between the plywood and the finished flooring isn't an option at this point.
Expanding spray foam seems like it would work well. I've seen attics done that way.
...Might be costly. Are there DIY kits available?

Glued, screwed, and/or taped foam board?
It would have to be attached well enough so that it wouldn't blow off going down the highway.
What are your thoughts? What have you done?
Thanks
