The difference between the Flexible Shipping and Cart Weight plugins is that the Flexible Shipping checks what’s the weight of each single product currently being in the cart and then sums up their total weight. The Cart Weight, in turn, does not sum up the weight of each single product but takes the weight value served directly by WooCommerce via get_cart_contents_weight
.
If the Flexible Shipping plugin’s weight-based rules recognize the products’ weight properly, it means that the WMPC plugin uses the woocommerce_cart_contents_weight
filter to add the calculated weight value, which comes into play later than get_cart_contents_weight
used by the Cart Weight. This is why the Cart Weight does not see these modified later weight values coming from WMPC.
Since the Cart Weight uses the WooCommerce default mechanisms, and WPMC modifies the weight non standard way with the filter, I’m afraid that in such case the WMPC would need to change the way how they weight values are applied by their plugin to make these two running well together.
Kind regards,
Luke