Just how much stronger is a full dimension of 2"'s (rough cut plank) over the finished dimension of 1.5" of finished planks. Where I priced finished lumber the other day, the finished dimension was 1.5 " verses 1.75 's a few years ago. Have span tables been adjusted down for the reductions in finished lumber dimensions ? How would I calculate the increase in the span of a full 2 X ?