change grid

Hello,

I’d like to change the space between the grid colums (to 2%) in order to get a tighter lay-out. I started to change the grid in the customn css but can’t figure out the way of calculating percentages of the multiple column grids. (see below). Only change the grid width to 2% doesn’t work because an image of 1/1 above 2/3 and 1/3 don’t have the same width.

div .av_one_fifth {
margin-left: 2%;
width: 18.4%;
}
div .av_one_fourth {
margin-left: 2%;
width: 23.5%;
}
div .av_one_third {
margin-left: 2%;
width: 32%;
}
div .av_two_fifth {
margin-left: 6%;
width: 36.4%;
}
div .av_one_half {
margin-left: 2%;
width: 49%;
}
div .av_three_fifth {
margin-left: 6%;
width: 57.599999999999994%;
}
div .av_two_third {
margin-left: 6%;
width: 64.66666666666666%;
}
div .av_three_fourth {
margin-left: 6%;
width: 73.5%;
}
div .av_four_fifth {
margin-left: 6%;
width: 78.8%;
}
div .av_one_sixth {
margin-left: 6%;
width: 11.666666666666666%;
}
div .av_one_seventh {
margin-left: 6%;
width: 9.142857142857142%;
}
div .av_one_eighth {
margin-left: 6%;
width: 7.25%;
}
div .av_one_nineth {
margin-left: 6%;
width: 5.777777777777778%;
}
div .av_one_tenth {
margin-left: 6%;
width: 4.6%;
}