I've just added some larger oak hardie blocks to the shop. The main size I use is 9"/22cm high, stand it on a small oor table and it's fine. The real advantage is that, if you've a lot of material to cut then it's a good height to use if you're sitting on the floor (the most comfortable and practical position for doing this).
These higher ones also come with a galvanised steel handle on one side. Easier to move around and makes a secure holder for the hammer when not in use.
The page is here