Customer pays only for highest weighted object

Hi Guys
Have been scouring this site for a while, and managed to solve all but one of my issues :)

I am using the "Zone rates" shipping module in Zen Cart. I have created and defined two zones, one for all of AU (Australia) and 00 (Everyone else). These zones seem to be working OK.

However, I sell very light paper graphics, however their dimensions determin the postage cost.
What I have attempted to do is:

So you can see I gave the graphics a weighting of either 0,1,2,3 to charge the respective cost.

However, the problem is:
When a customer orders 2 large graphics.. they should only be paying the single cost of 1.40 (or 7.00 for overseas). However Zen Cart is adding 2+2 = 4 weight and therefore charging $9.00 .

Desired solution:
I only want a customer to pay a single shipping cost - based on the largest/heavist item.

Any pointers or tips? =)
Much appreciate any help.

*Zone 1 Shipping Table - AU: 0:0.00,1:0.60,2:1.40,10000:9.00 *

Zone 2 Shipping Table - 00 (everywhere else): 0:2.00,1:5.00,2:7.00,10000:15.00

:O
Of course i get stuck for hours hence made my first post... however 5 mins after posting, I think i have a solution which seems to be working! I am posting this to gather more ideas, or share a solutiong with anyone else having this issue.

I am now using the following in my Zone tables.

I then need to ensure i weight my items correctly when i create the products
0 for free items
1 for anything that fits into a small graphic envelope for 60c (this allows up to 199 small graphics for just a single 60c envelope)
200 weight for anything that fits into a large envelope (this allows a couple dozen graphics and any small and medium graphics get caught up in the 200lb to 5000lb envelope.
and anything xlrge gets a weight of 5000 which results in the highest charge.

This seems to be working :)
a) does anyone know of an easier way to do this
b) do you think i might have any issues using this technique? (besides the fact someone can order a couple dozen large graphics, which should cost $1.40, but may push them into the next bracket.)

I order 1 medium I pay .60

I order 1 xlarge I pay 9.00

What if I order 1 medium and 1 xlarge?

What if I order 100 medium?

What if I order 100 xlarge?

What if I order 100 Medium and 1 xlarge?

What if I order 100 Medium and 3 xlarge?

deezee:

a) does anyone know of an easier way to do this

Yes.
http://www.zen-cart.com/downloads.php?do=file&id=899

This module is very scaleable. All you need to is enter correct weights and dimensions for your products and the module will provide accurate quotes from small letters through to courier parcels based on the items placed in the cart. It tries to fit the items in as small a parcel/envelope as possible.

deezee:

b) do you think i might have any issues using this technique? (besides the fact someone can order a couple dozen large graphics, which should cost $1.40, but may push them into the next bracket.)

I think a review of Ajeh's latest reply is sufficent answer to this.

Cheers
Rod