Resizing Related products/ more than 4 col

I need to resize or make the Related products smaller by making them be 5 or 6 on every product page (at bottom)for example: I have tryed to edit the Theme Functions, tryed adding a custom CSS, but it just wont work
http://impulsionstore.com/shop/all-match-solid-color-long-edition-long-sleeves-slimming-coat/

Thank you very much!