Sure, but like I said, you should go in with your eyes open. The fact that it is specified as implementation dependent, means that even a single implementation might quietly pack different structs differently in different circumstances, and you could happily carry on for years before discovering it. So the fact that it works for you today, is not a complete test.
It's a different story if the compiler vendor exposes, documents and guarantees the implementation, then you can be sure. But I think this is not typically the case. The whole thing rests on how much certainty you need.