Recently, I was invited into a local post office. I had the opportunity to watch as one of the clerks sorted parcels to the routes. They had large plastic rolling hampers spread around (each hamper goes to a route) and a huge pallet in the middle where Amazon parcels that got drop shipped there for the final leg of the delivery by USPS was being worked. The clerk took each parcel and held it out (like beam me up scotty) and a large overhead scanner was able to capture the bar code and announced the route number. The clerk then threw the parcel to the hamper for the route that was announced. Yes, I mean THREW. And some hampers were 20 feet away. A few of the parcels were the size of small boomboxes and they landed into the hampers with a huge thud. It was very interesting but one thing came to mind. If you send a boombox out, and you did not cushion it bulletproof. I mean literally bulletproof, your boombox might not fare very well upon delivery. What happens behind the scenes at any of the delivery services might surprise you. Yes, the videos of the delivery person throwing parcels over fences gets all the attention and the uproar, but this same thing happens all the times in the processing facilities. They fall off conveyors, gets tossed around. Have large parcels land on them... whatever.
Bottom line is this. If you want your boombox to arrive safely, you really need to pack them really really well. And not only from crush damage, but also from shock damage. Even though outwardly, you may not see any damage, I'm sure boomboxes were never designed to survive 5G's of shock. Don't fool yourselves. Going with fedex or UPS doesn't guarantee that your parcels won't be dropped either. They also rely on conveyor sorting that simply terminates at a hamper where parcels drops in. If a hamper is full, where do you think the parcel is going to land? This type of handling probably isn't going to change anytime soon. In fact, with the growing reliance on internet sales rather than brick/mortar shopping, parcel handling is only going to grow over the coming years.
Armed with this knowledge, although it will cost you more to pack your boomboxes to survive this type of handling, you should be well ahead of the pack on boombox arriving safely. That is, if you take it seriously.