Help with table rate shipping

Hi, I have purchased the table rate shipping plugin as recommended here to fix my problems. I am finding it really hard to figure out but have almost acheived everything I want to. I currently have it set up so that the most expensive shipping method overrides everything else, and this seems to work up to a point.
This is what I have set up:

https://arbtalkmedia.co.uk/wp-content/uploads/2020/09/Screen-Shot-2020-09-20-at-22.13.55.png

Heres where the problem arises that i can’t find a solution for and would really appreciate some guidance.

Pallet is the most expensive shipping class, but for some items 1 item takes up an entire pallet so I need to charge per item. There is an resins shipping class on the list. Anything up to 3 items of this class has a regular shipping charge, whilst anything 4 and over is all shipped on a pallet. If I place 2 items with the shipping class(at ￡55 per pallet) in my cart it comes to ￡110. If I then add 4 cans of resin this should count as one pallet, giving me a total shipping cost of ￡165. However it classes each can of resin as an item, and charges ￡330 for 6 pallets.

nb. in the attached image pallet is set as a row cost. I had it set as an item cost when I was getting the above problem. I have tried various settings and haven’t come up with a solution yet.

Thanks!