zencart plays with my shipping data -Canpar

I've heard other people going through similar problems, and the fixes all seem to be just workarounds, so I'm going to give an explicit case and try to get a real solution.

Zen Cart 1.3.8a Patch: 1. with Canpar shipping module.

I can post the code, if you like, but it basically writes a url requesting shipping data, and then gets the XML response.

If I do this by hand, I get an XML with the correct pricing. But if I let the form do it, I get a totally unrelated price and there is NO logic to it.

I have the Package Tares set to 0:0, nothing fancy. I just want it to use the information it gets back from the XML and not play with it. How can I do this?

Thanks in advance.
P.S. an otherwise excellent product, it's just that this is driving me nuts.

Just so you can see what I'm doing, the guts of the shipping module are thus:

//Connect to CanPar here to get quote, and parse XML.
      $request = join('&', array('service=1',
                                 'quantity=' . $shipping_num_boxes,
                                 'unit=K',  //Weight is in Kilos
                                 'origin=' . $srcFSA, //postal code of the store
                                 'dest=' . $desFSA,  //postal code of the buyer
                                 'cod=0',  //no COD charges
                                 'weight=' . intval($shipping_weight), //Interger weight
                                 'put=0',
                                 'xc=0',
                                 'dec=0'));
		
	  $body = file_get_contents('http://www.canpar.com/CanparRateXML/BaseRateXML.jsp?' . $request);
      $body_array = explode("<BaseRate>", $body);

      $ShippingCost = $body_array[1];
      $ShippingCost = ereg_replace('</BaseRate></CanparCharges></CanparRate>', '', $ShippingCost);

This writes a URL something like:

http://www.canpar.com/XML/BaseRateXML.jsp?service=1&quantity=1&unit=L&weight=10&origin=M4X1W7&dest=L4Y2N9&cod=100&dec=200&put=0&xc=1  

if I write my own url, I will get back XML data like this:

<?xml version="1.0" encoding="windows-1252"?>

<CanparRate xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="http://www.canpar.com/XML/base_rate.xsd">

      <CanparShipment>

            <COD>0.00</COD>

            <Declared>0.00</Declared>

            <Origin>M4X1W7</Origin>

            <Destination>L4Y2N9</Destination>

            <ExtraCare>0.00</ExtraCare>

            <PUT>No</PUT>

            <Quantity>1</Quantity>

            <ServiceType>1</ServiceType>

            <Weight>10</Weight>

            <Unit>K</Unit>

      </CanparShipment>

      <CanparCharges>

            <BaseRate>[B]8.65[/B]</BaseRate>

      </CanparCharges>

</CanparRate>

and yet, Zencart will NEVER give me a value of 8.65 for shipping.