I would agree with the statement about the power hammer and a ratio. Is an important factor. and a power hammer can hit a lot harder than a human. That is why it is called a mechanical advantage. Anvil size is not as critical. First Frosty will like this I went to the Juno museum of history. There is a blacksmithing display with tools and photos. Anvil and all tools had to be packed in so every thing was small the anvil weight was 50 pounds. the bellows was small also the tongs ans other items were regular size. Not only did the shoe horses but they fixed mining equipment of the time. The Earth as a whole is the Heavy part of this planet if your anvil is connected to earth than you have all that mass behind it. Now look at Brian Brazeal's striking anvil. I made one in total it weight is 60 pounds and I use a 16 pound sledge hammer on it. the area of the shop where I have used it for the last 3 years the sand under the pavers has been compressed about 1/4". When I do demos I use it first because it is easy to move around. second if I have students striking its not my good anvil and if they miss and hit the face, its only mild steel. I have forge 3" stock on it with no problem. I do not have anvil envy. Its not how big it is it is how you use it.