I went ahead and picked up a few of the tins from Specialty Bottle to see how they work as tea tins. I got TND1-TND16, as well as TWS6. Here is what I found.
Stacking with self:
All of the containers stacked okay with themselves. This means that you could stack them and they will sit flat on each other. However, if they are jostled, they may topple over. The TND's all stacked up to 4 high, while the TWS6 will only stack up to 2 high.
Stacking with others:
All of the canisters stacked okay with the canisters larger than them. However, some stacked particularly well, not toppling even when jostled. The TND1 is best on top of the TND2. The TND6 is best on top of the TND8. The TND8 is best on top of the TND16. The TWS6 is best on top of the TND4 or the TND8.
If your shelf space is right around 6 or 12 inches high, the TWS6 is probably going to work best for you. If your shelf height is about 7.75", a combination of TND4's & TWS6's will probably be the most stable. For any other shelf space height, it is probably better to use another canister and/or a mix of canisters.
For those who want to replace their Adagio sample tins with something more stackable, the TND4 and TND6 will work best.
For more information, including capacity, please see the complete review.