Scioly.org

You should add those horizontal trusses at base as well. Just like at the top. To save more weight, you can just use Z bracing for the whole tower instead of Xs. It is actually a bit more efficient in my opinion. So for example, with 9-10 z trusses on the base, you would probably use up the same amt of wood. and same for the top

I might try Z bracing for the top, but for the bottom, it is fine. I tested just the base for this design and it held the full 33 pounds for a while. The main problem is the connection and top.