Australia Post charge by a cubic cm converted to weight estimation method for larger boxes of a regular shape as do other couriers. They do this because carrying large light parcels is not exactly profitable - can you hear the violins .... ooohhh poor them. Unlike the courier companies who measure irregular objects as if they were in a box and then convert it to kilos, if Australia Post get an irregular shaped package they revert to putting it on the scales!! See where I'm leading.... take this example:
Toll/IPEC Freight Shepparton to Perth
Aust Post
Aust Post again
Odd Shaped box for fuz 7 regular shaped box with wing for 1 .2m PSS model.
After measuring cubic volume of <2.0 kg of parcel they convert to an estimate of the weight they could fit in that volume. Estimate in this case 30kg
Freight Cost by road $59.00
Same package treated as regular (ie rectangles and squares) boxes and measured for volume.
Box 1 $20
Box 2 $18
(Express Post $49)
But this time a custom made (took me about 1/2 an hour) 5 sided box to fit fuz (hence irregular shape) taped onto box 2 (a rectangular box containing the wing) to make only 1 extremely irregular shaped package weighing <2kg
Total Postage $18
My box - fuz box taped on top of wing box - this is then treated as one package.
Therefore pack your models well in the most unusual box you can easily make and save :o) DJ