Shipping Single Item, Multiple Boxes/Weights

Hi all. One of the items we sell is furniture that ships in multiple boxes, for example: table top in one box, legs and hardware in another. It is sold as one item, of course.
Problem: each box needs its own shipping cost. A combined weight may be 42 kilograms, which if it was a single box would cost, say $50 to ship. But since it comes in two boxes, each box costs $30 to ship for a total of $60.
Since a Zen Cart Product only has one weight field, the customer only sees the $50 shipping charge on their bill, and we have to phone them to request the additional $10.
Is there a way to indicate multiple packages/weights for a single Product?
Can I put each item in as a separate Product and automatically add the "legs" Product to their order when they buy the "table top" Product, in such a way that shipping will be calculated for each item individually and not just combine the two weights into one total weight?
Or is there a plug-in that can handle multiple weights?
Thanks!

What method are you using to determine shipping cost?

kobra:

What method are you using to determine shipping cost?

Hi Kobra. Currently we use Zone Rates (Modules/Shipping menu) and it's set to price with Shipping tables for each zone, for instance:

49.99:9.99,99.99:12.00,299.99:16.00,999.99:25.99,5000:0

so anything up to $49.99 has a $9.99 shipping cost, anything between $50 and $99.99 has a $12.00 shipping cost, etc.

So really, is not an accurate way to ascertain true shipping costs, given that some Products are heavier than others of the same size, while others are light but much more bulkier. We can easily reduce the costs charged to the credit card or Paypal if the actual shipping cost is less, but no way to increase it without their permission.
I would like to install the Canada Post shipping module when I get the chance to upgrade our store to a newer version of Zen Cart, which could then ascertain a more-accurate shipping cost based on both weight and size. But even there, I don't think there is a way to indicate that a single Product has multiple boxes.

Now, under Configuration/Shipping menu item, I do see a "Display Number of Boxes and Weight Status" setting, which currently is set to 3 (Both Boxes and Weight). But, I don't see where that gets used - does it only get displayed if our shipping method was set to "Per Item" (item) or "Per Unit" (perweightunit)? And would that give me a way to say that this Product comes in two boxes, one of which weighs 32 kilos and the other at 10?
Thanks!