Using a PVC tube is great when you're shipping something like a cue, but the added cost would put shipping too expensive when shipping just a shaft like we often do. Here's a few things we've learned over the years.
1. Insurance is only good up to the actual value of the product. You can't ship a $500 cue insured for $1000 and expect to get $1000 if it's lost or damaged. They will ask you to justify the value.
2. Triangular tubes are better than square boxes as long as they are the heavier duty ones like UPS and Fedex provide. The ones the post office provide are junk.
3. Round tubes are fine, but they need to be heavy duty. The thin ones are junk.
4. When shipping cue shafts, wrap the shafts in padding, but always leave room around the padding for the shaft and padding to float around inside the box. Long tubes or boxes are often "bent" as they get caught up in machinery. If there's sufficient room, the box can bend a fair amount before it actually bends the shaft inside. If you pack it tight, the shaft will bend with the slightest amount of bend to the box. If you still get a bent cue shaft, they most likely will deny it due to "insufficient padding". But, always appeal it to the next level. Explain why it's packaged the way it is, and also explain that the damage the shaft received is not caused by insufficient padding, but rather it was caused by the box being bent. We've always been paid when this happens.
5. If a box arrives damaged and you make a claim, you must always keep the packaging. They will most likely want to come pick it up, and they will want the packaging.
6. If you're shipping something of significant value like a high dollar cue, the insurance most likely won't help. All shipping companies see these items like "works of art", or "antiques" or "collectibles" etc. These kinds of things are not insurable by their means and you should find an alternative insurance coverage for them. I know some high end cue makers who have a special rider on their business liability coverage. It's the only way I am aware of to get coverage for expensive cues.
I hope that helps!
Royce