Yes, you really do need to run multiple windmills to get a useful power setup. You could mod it will Millwright, it uses more materials for for bigger sails. I do find it a bit more powerful by default then vanilla so I edit the .json to make them comparable. I usually run 2-3 helve hammers on a single anvil though. There is no need to build the windmill that high, modded or not. You are better off spending your time finding more flax than getting more resources for more axles. You don't need to use the large gear if you only have one windmill. It's a resource saver when you are just starting out, and you are probably already aware of this, but you can string the helve hammer, polarizer and quern off of the same gear. I remember reading that the more parts you add to the system, the more it slows it down. Height does still make up for a bit for this, but not enough to run one sail. Good day.