And with a ten frame deep langstroth box full of honey you have a box that is about halfway between arms length and at your body. And you have to handle it anywhere from the ground to over your head and it weighs (full of honey) 40kg (90 pounds) when it isn't glued to the box below. After you pry it loose, it glues itself back down so you may be lifting 80 kg (180 pounds) until it lets go again. The eight frame boxes have eliminated the two frames furthest from your body (the ones with the most mechanical disadvantage) and you have a lighter box that gets glued back down less (because of less weight). The eight frame medium full of honey weighs 22kg at the most. And if you look at the above chart, that's still on the heavy side...