Pallet Shipping Based on weight of an item

Hi,

I'm using Power Store 3 and try to add some extra shipping rules with eCart.
I have large and heavy items in the store which need to be shipped on a pallet. So what I want to apply is the next:

If a customer orders an item which is heavier than 25 kg than this item needs to be shipped on a palllet with extra shipping cost of 40 euro. So far not a problem at all.
But if a customer orders multiply of these kind of products than these extra shipping costs need be applied on every heavy item.

For example >

if customer orders the item a (30 kg) he needs to pay 40 euro extra.
if this customer oders more items which are all above 25 kg each than he needs to pay 40 euro extra for each item.

How can I set up a shipping rule in eCart to achieve this?

Regards.