Not sure, but consider this before you drill... Top Fin tanks used to carry a lifetime warranty if you used their stand. If you got this from Petsmart you likely received it as the stand tank combo. If it still carries the same warranty you will void it if you drill it.
The reason I mention the warranty is because I had a 120g Top Fin crack its frame. Two years after buying the tank I called the store and they had me return it with a choice of a FULL refund. So I would think twice about drilling if they still warranty the product the same.