spraying foam insulation between the ceiling and roof works great. I did this on a crew-cab by drilling 1/4" holes every 6" on a cross section and holding the plastic tube in one until foam was forced out the surrounding holes then move over and repeat. Next day cut off excess with razor blade and throw away the shirt you were wearing.My roof is like a igloo cooler lid.......ps. be sure you set your bit so you can't drill through, I don't think you have 2" good luck
