Hi,
It is indeed impossible to take into account custom item fields for shipping method costs calculations. What I described in my previous message is only possible if you use a characteristic with variants for the item size selection.
What you could do is to use the cart fee plugin:
www.hikashop.com/marketplace/product/279-cart-fee.html
With it, you can add extra fees to the cart.
For example, you could configure it:
- with a condition: {itemsize}>36 (where itemsize can be replaced by the column name of the custom item field)
- with the logic "OR"
- with a formula like: {price}*0.15
However, this will take into account the subtotal amount, so the 15% fee will be calculated on all the products in the cart.
If you want a 15% fee calculated only on the total of the products with an item size > 36 where the item size is in a custom item field, the only solution to get exactly that is to develop a custom plugin.
If that's something you want us to work on for you, that's possible. You can request a quote via our contact form:
www.hikashop.com/support/contact-us.html