Any way to include packaging weight in shipping weight?

I'm setting up a new site with OpenCart 1.5.1.3, and am gradually refining the shipping functionality to fit my requirements.

My problem is trying to find a way to allow for packaging weight in the shipping calculation. I'm going to be selling CDs and LPs, and use padded envelopes for CD-only orders, and for LP orders I use heavy duty cardboard LP mailers which can accommodate several LPs and CDs. This means that the packaging weight varies as follows:

- If order contains 1 or more CDs ONLY, add 50g to total weight (regardless of quantity)
- If order contains 1 or more LPs, or a mix of LPs and CDs, add 200g to total weight instead of 50g (regardless of quantity)

So I'd like to know if there's a way to allow for packaging weight, based on the category/categories of products in the order? Or perhaps by including some kind of custom attribute on the products themselves (e.g. 'packaging type: Padded envelope / Vinyl mailer') that somehow feeds in the appropriate packaging weight into the shipping weight total?

Thanks for any advice you can offer!

I'm struggling with the same problem. I also sell vinyl records and CD's
Like you I work on the assumption that the average 7" single or CD weighs 50 grams and 12" singles or LP's weigh around 200 grams
The problem I am having is that if a buyer orders multiple items my fee structure then becomes disproportionate
The first items always weigh more and so you cant just charge per 50 or 200 grams
I hope you get my drift
I'm looking for an easy to understand extension that will make this possible
I'm using version 1.4.9.4.
So far I have been recommended
http://www.opencart.com/index.php?route ... on_id=2684
but to be honest I'm a bit lost with the programming language
I don't want to throw money at something I don't understand or do anything to upset my opencart as it is

Please let me know if you find a solution. I'll do the same for you

I think there is a module that can solve your need "Category Based Shipping" . I am using it and I am almost certain that you can use it for your purpose . Visit www.getclearthinking.com . The site owner Johnathan is a very helpful guy . You can confirm the same from him by using the contact tab on his site and then go ahead and buy that module .

There is a specific provision in this module to add any % of your shipping weight as your packing weight . e.g You could set it to 10 % or 20 % . Also you can define different shipping rates for different categories and then take their sum , average or higher of the two .

This module is a life saver . No harm in visiting the site and taking a look at it yourself .