In theory by law, 0.3% or less should be ok. That said, I would advise keeping them in original packaging (preferably unopened) and not bringing any back. If you try to creatively conceal them and they get discovered, think they are gonna buy that they are 0.3% or less? Or might they believe you are bringing in something stronger and illegal? Risky.
In reality, there is always the chance you run into an unreasonable authority and get screwed regardless. In general, I think traveling with this stuff and putting yourself at the mercy of random law enforcement in foreign countries is an unnecessary risk. The vast majority of the time, it's probably fine (hence you'll see anecdotes of people who did similar with no issue), but the chance you become an exception can really **** things up royally for you.
