Aaaaaand, further testing, at least with my version of Apoc, confirms that the formula above is correct, as well as that Roger Wong guide is wrong (again). There is no "weighted" encumbrance, every item just adds it's weight. I checked with medikits, laser rifles, armor, stun grapples - everything just adds it's weight to the encumbrance (I've confirmed encumbrance values with Apoc'd as well as ingame speed display - for example, medikit + 3 grenades equals a megapol helm, 3+3x2 = 9) As to why they add 1/2, I have no idea. Must be an oversight in the original formula. Maybe they just wanted to ensure it's rounded, not truncated?