CMS Designing new grid
 

I've read about the fact you can flatten a grid in order to build your own one.

How easy is it to build a new grid and how far can you go with it?

The default ones at the moment have anything from 1 to 3 columns of different sizes etc. Is it possible to get rows aswell as columns. So for example, I could have 1 row at the top of 100% width. Then 2 coloums below with 60% and 40% width and then finally another row at the bottom with 100% width?