My filler says to use a 4" strip on a 4" diameter pile of filler. It also says 2-3%, but not how tall the 4" pancake is. I have had to throw out filler because it does get too hard to spread too quickly. Seems like that only takes a few minutes or less to happen. Am I using too much hardner or just mixing up to much filler? I did try about 3 or 3.5" strip and it didn't make much differance.