Is it only the bumperstop category? If those products were consistent between the sort order of the "Shape" and "Bumperstop Color" attributes, there would be a solution using only CSS to "hide" the Shape information. For example, if the Shape was always the first attribute in the sort order (like your /index.php?main_page=product_info&cPath=20&products_id=218 product), you could create the file /includes/templates/abbington_mega/css/c_20.css (so it will only activate for the bumperstop category) to contain:
Code:
#productAttributes h3+div { display: none; }
That tells the browser not to display any <div> that directly follows an <h3> within an element with id="productAttributes".