Best way to add XL-column SASS?

There are a few options I've found on the web to add an XL column (i.e. 1200-1600px or min:1600px), such as link link 1 and link 2, but they do not mention Mendix. So before wasting my time, does anyone have a clue what the best way is to add additional column classes, such as XL and XXL? For instance, I've got a 8/4 grid that looks nice on 1200px screen, but on a 1920width screen it looks horrible and 9/3 would be better..
1 answers

The column widths in a layout-grid are coded in bootstrap.

Can upload a screenshot of what you currently have?