Linking UPS calc with discounted rates?

So, I've scoured the forums for my problem, but I have found no solution, and now I turn to you, fellow forum freaks, to help me with my problem.

So here's the situation; our website, which is running the latest version of ZenCart, using UPS for our primary method of shipping. We only have ground shipping available to us, and we have set up the UPS shipping module to handle said speculations of where the package is coming from and where it is going to.

We've had a couple of sales already, and the shipping calculator seems to work and integrate a final shipping cost to our customers, but on our Daily Pick-Up, our prices vary greatly from what the value is that the shipping calculator is grabbing from UPS' website.

We apparently get a discounted price through UPS shipping, but for whatever reason, the price returned to the end-user is less than what we are paying UPS. In otherwords, we are losing money for each item we ship because UPS is returning a value that is less than our pro-rated value.

What the hell can I do to make my shipping calculator return the correct estimate for the user?

Could you give an example of a Ship From and Ship To and the weight where this is happening?

I'm going to jump in here since I'm seeing the same thing as Siberkil. I was just analyzing my shipping costs and saw it. Here are some examples (all ship from zip 55432):
to zip 73742, actual weight 1 lb (weight used in shipping calc was 2.5 lbs)
to zip 64428, actual weight 6.3 lbs (weight used in shipping calc was 10 lbs)

My UPS is set to ship to commercial addresses, but I know that the second address above was residential. So I'm thinking that was the problem with that address, but it doesn't explain the first.

The weight used to calculate the shipping charges is off in both examples, as you can see (mostly because I'm guessing at the weight when entering them into the system). But even with these inflated weights, I was still short over $4 for shipping on each.

Thanks for any light you can shed on this!

--Greg

What are your shipping settings that result in the weights:

to zip 73742, actual weight 1 lb (weight used in shipping calc was 2.5 lbs)
to zip 64428, actual weight 6.3 lbs (weight used in shipping calc was 10 lbs)

I'm not sure I completely understand your question, but I am not using the tare weight calc (they are set to 0). Those are the weights of the products that they ordered. Does that help?

--Greg

What does actual weight 1, weight used in shipping calc 2.5 mean?

How did it go from 1 to 2.5 lbs if your Tare is 0:0 ...

What do you have set on the Maximum Weight shipped?

Sorry, I'll clarify. When I said "weight used in shipping calc" I mean the weight that I entered for the product. In this case, when creating the product I entered a shipping weight of 2.5 lbs (I didn't know the actual weight of the product). When UPS go the package, they weighed it and determined the actual weight to 1 lb.

Thus, Zen Cart used 2.5 lbs to calculate the shipping cost that was charged to the customer. But in reality, the package weighed 1 lb.

Even with that discrepancy in the weights, UPS charged me more for shipping than Zen Cart calculated.

Sorry I wasn't clear the first time. I hope I did a better job in describing the problem this time around.

--Greg