Let me describe my development environment first;
2. Genesis framework (latest version)
3. Enterprise child theme
4. WooCommerce (latest version)
5. Page type - full width
This is a problem that many people seem to have, with no viable solution.
On category listing pages, or likely even the default shop page, there are rows of product thumbnails. In my case there are 4, and I would like to increase that number to 6.
WooCommerce has a document here; http://docs.woothemes.com/document/change-number-of-products-per-row/ that shows you how to achieve this.
Unfortunately, that code only works if you want to "decrease" the number of products. For example, if you change it to 3, you get product thumbanils on a row, whereas if you change it to 6, you still get 3 product thumbnails.
It is unclear if the theme is causing the behaviour, or WooCommerce. Well, not entirely true, you can see the same behaviour if you test it with the default WordPress theme Twenty Twelve which makes one think the behaviour is originating in WooCommerce.
Part and parcel of this problem, is the size of the thumbnails. If you test this on a page with a sidebar, the thumbnalis are considerably smaller, which makes one think the thumbnail size is dictated by the page width (i.e. 100%).
I figured, by using the WooCommerce code sample, and changing it to 6, ona full width page, the thumbanils would scale down and the result would be 5 across but the thumbnails do not scale down, and even worse, after the third one, they wrap to a new line.
I have yet to find anyone has solved this problem, and am reaching to this community with my fingers crossed in hope of a solution versus the wordpress support channel here on wordpress.org, because to be honest, it is unclear if it's a woocommerce issue, a theme issue, or a wordpress limitation.