Absolutely top quality product. I did have a bit of a struggle  inserting the umbrella mast shaft into the base support shaft. It took some wiggling n effort, but then it fit perfectly. 
I did it as a 1 man job. All the parts are quality. There is even a cover included that it's great fabric and covers the entire product. 
Yes you need to buy the weights to hold it down. Cantilever by definition means a load ( the umbrella) supported at the opposite end. So Yes its off balance . A worthwhile investment for an expensive quality product.