I want an option to compute the shipping rate for 24 kg products.
The first 4 kg will cost 8 euro, the next block of 4kg will also costs 8 euro.
So far, the default shippingbyweight plugin has Rate per weight unit but it counts 1 unit = 1 kg which fails for me in this situation.
I've extended the plugin to add in UnitBlock field to allow admin to define how many kg/lbs will be counted.
order weight from 0
order weight to 100 (kg)
Additional fixed cost =8 (euro)
Low weight unit=4 (kg)
Unit block = 4 (kg)
Rate per weight unit=8 (euro)
So, for 24 kgs, the shipping fee will be 8 + 8*5 =48 euro.