Product shipping weight problem

Hi! I have a Norwegian shipping module which calculates the shipping cost from the products weight. My problem is that the volume weight of some of my products are way higher than the actual weight. But if i sell two of theese products together the volume weight stays the same. Because of this i cant put the volume weight directly on the product.

An example:

one product:
volume weight: 1,5kg, actual weight: 0,5kg
two products:
volume weight: 1,5kg, actual weight: 1kg

What is the best way to solve this?
I do sell other products aswell so i cant use fixed prices.

Check settings in the admin > config > shipping
For small package tare
Use actual products and add packaging weight as tare

What if the customer doesnt buy any of the products with big volume weight, but other products? Then package tare will be added and the shipping cost will be expensive when it shouldnt?

What if the customer doesnt buy any of the products with big volume weight, but other products? Then package tare will be added and the shipping cost will be expensive when it shouldnt?
That is why there is small package settings and large package settings

I'm not shure if you understand my problem correctly.

Scenario 1:
The customer buys regular products whith a total weight of 1kg. The shipment costs will be 1kg.

Scenario 2:
The customer order one "high volume weight"-product:
the actual weight would be 0,5kg but the weight i'm acutally paying the post office for is 1,5kg because of the package size.

Scenario 3:
The customer order two "high volume weight"-products:
the acutal weight would be 1kg, the weight i would pay for is 1,5Kg because the two large products will fit the same box.

Scenario 4:
Customer buys one regular product and one "high volume weight"-product:
The actual weight is 0,6kg, the weight i'm paying for is 1,5Kg because theese to products fit in the same box.

The best solution of my problem:
if there is one or more "high volume weight" products in the shopping cart the weight of the shipment should be 1,5Kg (or more if the actual weight is more)

An alternative solution:
if one or more of the products in the cart is a "high volume weight" product, add 1kg to the shopping carts total weight

Hope im expressing myself clearly now.. :P

If not displaying weight to shoppers one can adjust weights to achieve cost for shipping

Or there is a commercial shipping module that many are using

kobra:

If not displaying weight to shoppers one can adjust weights to achieve cost for shipping

Or there is a commercial shipping module that many are using

I am not showing weight, but if I adjust the shipping weight and then buying two of the "high volume weight" will result in a 3kg shipping cost... thats too much.. commercial shipping module? hm. search

commercial shipping module? hm. search
Google "zencart advanced shipper"