Great article, but would drugs not contribute more to the bodybuilder's size once you adjust for skeleton and organ weight?
It appears you arrived at the 30-40% improvement figure as the difference between a maxed out natural and a maxed out juicer (280lbs - 185lbs = 95lbs; 95lbs / 280lbs = 33%).
However, if you assume that both bodybuilders have about 100lbs of skeleton and vital organ weight (just for ease of running the numbers), the difference drugs make is considerably greater.
Let's assume that drugs predominantly grow muscle (there may be some visceral organ growth or bone density increase, but let's assume this is minimal). In which instance the difference is between a natural bodybuilder carrying 85lbs of muscle (185lb total bodyweight - 100lbs of skeleton and vital organs) and a juicer carrying 180lbs of muscle (280lbs total bodyweight - 100lbs of skeleton and vital organs).
The difference in actual muscle carried would be 111% ((180lbs of juiced meat - 85lbs of natural meat =95lbs) / 85lbs = 111%). A massive advantage.