Increase decrease the width of the two sidebar

I purchased the theme ligth cafe, I am very well, but I was wondering if it was possible to change the layout and put two on the right sidebar, but of different sizes, for example a sidebar 180 px and the other sidebar 260, leaving unchanged at 650 px (or reduced slightly, for example to 600) the size of the post. I was wondering if these changes could have a negative impact for the mobile version.
Thank you and I apologize for my bad English.