Just moved over from my "antiquated" GoDaddy shopping cart and the lack of dimesnional shipping is killing me. I have over 150 products with sizes from one square inch to 8' x 4". Having one default package size is a joke.
A quick search shows we have been complaining about this for many years. My old GoDaddy cart had a weight and dimesnions for every item, the dimensions of all the boxes I use, and would "pack" the boxes accordingly. It was light years ahead and was in 2012 when I started with them.
Not to beat a dead horse as I know this has been discussed to death but whats my best fix until I decide if IM even staying with Shopify? I see apps like Boxify, SHipping Rates Manager, etc. I need it to know what boxes I have and what will fit in them.
The app we develop, Advanced Shipping Rules, allows you set different package sizes for different groups of products. You can also determine different packages based on QTY of items beloing to that group.
I hope you would have found a solution to this. If not, You can use the Multi Carrier Shipping Label app that will help you handle the packaging process with ease. There are multiple packaging methods that are based on the weight & dimensions of your products. You can create custom boxes based on the product dimensions and the app will help you get the shipping rates accurately.