Heating blankets are designed to reflect and hold heat. Bad idea from the beginning IMHO.

Car dashboard light reflectors work much better and I find 4ftx4ft ones at the dollar store fo a dolla. They are much thinner than mylar and only designed to reflect light.

But white paint is by far the best option. Painting is fun! And it is super cheap. I only use the car dashboard reflectors to cover up light leaks and other things needed to be covered that I can't simply paint white.

Good luck and keep us updated bro!

Peace

O yea, the point of all that was to ditch the mylar and then use dash reflectors for everything you can't paint white, after you are done painting your cab white