Just sent mine with ups via parcels2go after asking specifically about shocks and pointing out it was considered dangerous by royal fail.
I asked the woman in the post office as well. She just said to call the help line. They were no help. It was okay, then I asked for a name or reference in case it was seized and suddenly it wasn’t okay to send. The lady on the phone became very confused when I asked if I could post a party baloon or a bicycle tube as both were capable of carrying a pressurised gas but currently didn’t, just like my air shock. The same shock, I pointed out, that regularly flies with easyjet and it hasn’t blown the plane up yet.
The only other conclusion I could draw is that royal fail are actually trying to go out of business.
Other than that, I have no strong opinion.