How to Increase the Number of Crosssell Items in Cart?

Question

I want to increase the number of cross sell items appearing in cart. The max item count is 4 in defined at app/code/core/Mage/Checkout/Block/Cart/Crossell.php

class Mage_Checkout_Block_Cart_Crosssell extends Mage_Catalog_Block_Product_Abstract
{
    protected $_maxItemCount = 4;

How can I increase this limit from admin end or set the limit in checkout.xml file.

Please Guide.

Thanks.