...Hm. That makes sense. Though the picture for the Armored Coat seems to imply that past the waist it only goes about halfway down one's hips. But even so, if it were to stack, then you have what's considered heavy armor for a +5 armor bonus to AC, a +3 Max Dex bonus, and a -2 ACP. At that point, you might as well just wear a Breastplate (+6 AC, +3 Max Dex, -4 ACP), because if you're wearing armor and carrying a board, chance are you aren't going to be making with the fancy acrobatics, climbing, or swimming anytime soon.