Configure UPS default packaging weight

[RodG]

So, a couple of questions on that subject:

1. Is it possible to change the default UPS packaging weight to 0? And if so, how?

https://www.zen-cart.com/tutorials/index.php?article=85

2. Do other shipping modules work in the same way?

Probably most, but not all... or maybe not :-)
It really depends on the module. EG, the Per Item method quotes are based on (wait for it) a specific cost for each item), therefore the tare weights won't make any difference.

3. Is there built-in support (out-of-the-box Zen Cart) for combined item shipping in Zen Cart? If so, how do I set it up?

Yes. This is zencarts' default behaviour.

4. Is there built-in support (out-of-the-box Zen Cart) for tube shipment? A lot of the items I'm shipping will be poster prints.

This is a *packing* issue rather than a *shipping* issue. Zencart (and indeed, any other ecommerce software) will have no concept of how you choose to "pack" any given item.

Cheers
Rod