I am getting ready to hang full 1/4 panel on my el camino and there is a spot or bracket just below roof line and above top of 1/4 that was filled with what looked like a type of foam. Mind was degraded to a point where I cleaned out bracket. This must serve as a stiffener for that area. Maybe dum dum is wrong word but what do you put in there that will compress w/ new 1/4. Most products I seen at paint supply store are of a two part type that mix's as its dispensed. I need something that stays someone plyable to give me time to set 1/4. I thought of filling it w/ 3M seam sealant but want to know if there is a specific correct product.
Thanks