Add Free Shipping Cost BUT based on Weight

[MrBaseball34]

Still struggling with this issue...
In Cart.php, around line 738 (PS v1.3.0.1)

$configuration = Configuration::getMultiple(array('PS_SHIPPING_FREE_PRICE', 'PS_SHIPPING_HANDLING', 
                                                 'PS_SHIPPING_METHOD', 'PS_SHIPPING_FREE_WEIGHT'));
// Free fees
if (isset($configuration['PS_SHIPPING_FREE_PRICE']) 
   AND $orderTotal >= floatval($configuration['PS_SHIPPING_FREE_PRICE']) 
   AND floatval($configuration['PS_SHIPPING_FREE_PRICE']) > 0)
 return $shipping_cost;
if (isset($configuration['PS_SHIPPING_FREE_WEIGHT']) 
   AND $this->getTotalWeight() >= floatval($configuration['PS_SHIPPING_FREE_WEIGHT']) 
   AND floatval($configuration['PS_SHIPPING_FREE_WEIGHT']) > 0)
 return $shipping_cost;

How would I modify this to return the shipping_cost if I had a PS_SHIPPING_FREE_PRICE
value of $100 AND PS_SHIPPING_FREE_WEIGHT of 20lbs.

I want the free shipping to happen ONLY if >=$100 and <=20 lbs.

My first thought was this but it didn't work:

$configuration = Configuration::getMultiple(array('PS_SHIPPING_FREE_PRICE', 'PS_SHIPPING_HANDLING', 
                                                 'PS_SHIPPING_METHOD', 'PS_SHIPPING_FREE_WEIGHT'));
// Free fees
if (isset($configuration['PS_SHIPPING_FREE_PRICE']) 
   AND $orderTotal >= floatval($configuration['PS_SHIPPING_FREE_PRICE']) 
   AND floatval($configuration['PS_SHIPPING_FREE_PRICE']) > 0)
   AND (isset($configuration['PS_SHIPPING_FREE_WEIGHT']) 
   AND $this->getTotalWeight() <= floatval($configuration['PS_SHIPPING_FREE_WEIGHT']) 
   AND floatval($configuration['PS_SHIPPING_FREE_WEIGHT']) > 0)
 return $shipping_cost;

Isn't it kind of idiotic to offer free shipping to where the total weight is GREATER than xxxx lbs?
I thought shipping was based on weight?

I would think that the free shipping that is based on weight should be calculated on if the total
was LESS than xxxx lbs.