I am having a heck of a time making scarf joints in the 4' of plywood. I am using my radial arm saw with a sanding disc attachment. It seems that as I am sliding the ply against the backstop, it is crushing the delicate feathered edge... is there a better way? I was thinking of switching to a hand plane method but it does not seem precise enough. Attached is a pick of my radial arm saw set up.