[dicer]

Too much spacing and what ever the stuff is inbetween the uprights, if it flexes easy and conforms easy, its going to lie to you . As it will easily conform to the cab top no matter what. Unless its some UFO memory metal of some sort? You'd be better off using plaster of paris, over some thin food plastic so it doesn't react something in the paint. You would need to make the mold in a thin strip of sorts, use clay to build the form to pour it into. After it drys you have your gauge. Even fiber glass could do the same.