WooCommerce Specific Category Columns Change

Hi WPMUDEV,
I have been trying to achieve a one column layout (product on left, price and description on the right) for a specific category (rentals) on our site. But no matter what solutions I try, it won't work.

add_filter('loop_shop_columns', 'loop_columns');
				if (is_product_category('rentals', 20)) {
					function loop_columns() {
						return 1; // 1 products per row
					}
				}

In the above code I am trying to specify is_product_category 'rentals', but it changes across the entire site??
Any ideas?

Thanks for your support!
-Luke