I have experienced both. Customs only searches 10% of stuff coming through so you have a 90% chance of it not getting opened / searched. On that note I have had it ordered three times and once out of three they snagged it because they stopped the box.
Let me help you some. I'm not saying this is right or anyone will do this for you but this is what people do for me when sending potentially stoppable stuff:
1. Label it something accommodating to the weight and sound when shaken
2. Label as Cordyceps, Milk Thistle, Beta Alanine or Creatine Monohydrate caps.
3. List correctly number of bottles contained in package
4. Ship on a Monday so it hits customs on a Friday afternoon
5. Ship with lowest price option with tracking number. No tracking may give better success.
6. Give cost below $50 and gift.