Wood is definitely better than nothing, but I don’t really see a situation in which this thing would need protection against small arms anyway. Unless something has already gone horribly wrong, those small arms are a significant distance from your artillery. At that range, they are already effectively worthless because their lack of rifling makes them horribly inaccurate.

If I had to guess, you would mainly be worried about union sharpshooters (maybe) and artillery. At that point the only real advantage of the wood is the obstruction of sight.