Just to correct you on this.

Shpping costs are calculated on weight/destination/ and to a lesser degree box dimensions**

** box dimensions are usually in tiers. Ie. If the box is over X dimensions it will cost an extra Y per kg. Often these dimension tiers are quite largr, so it is very unlikely the size of your box changed shipping costs.

Your cost will be set mainly on weight/destination/shipment and not on the size of the box.

How do I know this? I had to ship hundreds of items daily all around europe and I can confirm shipping isnt as straight forward as people believe it to be.