Sorry, but I am at a complete loss here.

My shipper charges a flat rate of $9 if my package is a specific size (10lx7wx3h to be exact). Each package can hold 2 items.

If a customer buys 3 or 4 items, the package size only increases in height (10lx7wx6h for example), and the cost from the shipper increases by $1, so if a customer buys 3 or 4 items, the shipping cost would be $10.

Maximum package size is 10lx7wx12h, which would be 8 items, $12 shipping.

How can I set that up in WooCommerce? And what about if/when a customer orders 9 or 10 (or more) items? Anything over 8 items would require an additional package for shipping.

Thanks in advance.