It`s simple to add a shelf and a ramp to a larger tank style cage. Many of us just buy one of those guinea pig shelters on legs, or make one from corner pine shelving that can be bought cheaply from Wilkinsons stores or any DIY outlet.
The mini Duna is becoming looked upon as a `starter` cage these days as people begin to realise that all hamsters require more running room so choose to go with a Zoozone 1 for dwarf hamsters, or a Zoozone 2 for dwarf & syrian hamsters alike. The word `starter cage` should be seen as a gimmick to buy something that is too small. Shops will always stock these as long as people buy them thinking they are a large cage. In comparison to the cages I mentioned, the little half shelf that the Duna comes with is no real substitute for more floor space. A shelf is a shelf really. I don`t recognise a shelf as making a cage bigger, but adding a vantage point. By the time shelving is added to a larger cage, it appears to make the cage smaller anyway due to the number of other accessories inside a cage.