im skeptical as to how much of a difference using a "silo" structure actually makes. it seems like 80% of seo is backlinks, 19% is putting keywords in the url, title , h1 tags, using a proper keyword density, and that sort of stuff. id guess that stuff like silo structures and internal linking are 1% of it at most. but i could be wrong, i havent done a ton of experimenting with internal linking so if anybody has any hard evidence that it makes a significant difference and is worth spending time on instead of backlinking, please share your experiences.