Ultimately, buying any drum that you have not inspected by hand, played in the shop, and been happy with there is a risky proposition.

You can minimize that by dealing with a reputable company, making sure that they have a return policy, being willing to pay the shipping costs back to them, and being diligent in communicating with the vendor, but again, you are far better served by only buying what you have played.

Personally, I have had virtually no dealings with buying online, but I am fortunate enough to be involved in the SCA community and belly dance community here in southern California, so I come into a fair bit of contact with shop owners and merchants that have the merchandise on hand.