that helped me a lot.
one problem i am having is different shipping rules overlapping.
for instance i have the rule for item 1 and 3 qty being <= 3 shipping is $6.50
another rule is item 2 qty = 1 shipping is $6.50
another rule is qty of unique items >= 2 shipping is $10.70
so if the cart has 1 of item 1 shipping is $6.50 and cart also has 1 of item 2 shipping is $6.50 and the combination of item 1 and 2 has shipping of $10.70, so total shipping is $23.70.