Technically...it would work. But.....
20 lb dacron is what I use on my warmwater rods. I tried superline (braids) as backing once. Never again. Sure, trout or panfish may never give you cause to see your backing...but there is a chance a big bass, catfish or carp might... braided superlines will slice your fingers up if you try to put pressure on the line while they are running. Dangerous and painful. Not worth it, to me.