Hmmm I might look into that insulation stuff.
Regardless, my recommendation is to undercoat with oil spray every fall. There are undercoating oils made for this that don't drip. I use the rust check stuff. It's well proven to do it's job.
I also spray some of the panel oil (also rust check) inside the doors and behind all the panels. Fair warning, that stuff is thinner and will drip. Park on a tarp for a couple days.
I also found that if you leave the can of rust check stuff open to air for a few days it'll thicken up a little and stop almost all the dripping