Shipping/Freight cost calculated by total weight not weight of each item (using mvs)

[myemin]

I have two item from different vendors , each one is 350 lb. using fedex freight method.

(RED)if I want to buy them individually one cost $436, the other $229.
(GREEN)if I want to buy them in one cart one cost $707, the other $316.
(BLUE)if I change their weight to 700 lb each and I want to buy them individually, one cost $707, the other $316.

The problem is that shipping cost is calculated by total weight (for each item) not weight of each item (for itself)(using mvs).

Is there any one who can help on that?

[myemin]

I am reposting this, because I think I was not clear in the previous post.

I installed Multi vendor system(I tried to follow all the steps for install, and now it is working fine till this point), and I was trying that with adding two different items. Each one is added for different vendor. (I have two different vendors)

Both items are the same weight, 350lb.

When I purchase separately it calculates freight cost in the correct way. (Freight for the first one is $229, and for the second it is $436.)

But when I put them in the same cart it calculates the freight differently as it were a weight of 700lb for each one (Freight for the first one becomes $316, for the second it becomes $707). I mean it use the total weight for each item, instead of using item's own weight. But it should be the same amount like I am buying separately.

I hope I am clear enough and someone can help me on that?

Thanks,
Jon