If anybody is interested in this, Ian Yates does a good job explaining it in this article/tutorial series:
http://webdesign.tutsplus.com/tutorials/complete-websites/building-a-responsive-layout-with-skeleton-widescreen/
It is simply a case of setting your desired min-width media query into skeleton.css and changing the values; either percentage of pixel-based. Here is mine as an example.
/* Note: Design for a width of 1400px */
@media only screen and (min-width: 1400px) {
.container { width: 1400px; } /*whatever you want - can even be fixed if you prefer*/
.container .column,
.container .columns { margin-left: 0.78125%; margin-right: 0.78125%; }
.container .one.column,
.container .one.columns { width: 4.6875%; }
.container .two.columns { width: 10.9375%; }
.container .three.columns { width: 17.1875%; }
.container .four.columns { width: 23.4375%; }
.container .five.columns { width: 29.6875%; }
.container .six.columns { width: 35.9375%; }
.container .seven.columns { width: 42.1875%; }
.container .eight.columns { width: 48.4375%; }
.container .nine.columns { width: 54.6875%; }
.container .ten.columns { width: 60.9375%; }
.container .eleven.columns { width: 67.1875%; }
.container .twelve.columns { width: 73.4375%; }
.container .thirteen.columns { width: 79.6875%; }
.container .fourteen.columns { width: 85.9375%; }
.container .fifteen.columns { width: 92.1875%; }
.container .sixteen.columns { width: 98.4375%; }
.container .one-third.column { width: 31.7708%; }
.container .two-thirds.column { width: 65.1041%; }
/* Offsets */
.container .offset-by-one { padding-left: 6.25%; }
.container .offset-by-two { padding-left: 12.5%; }
.container .offset-by-three { padding-left: 18.75%; }
.container .offset-by-four { padding-left: 25%; }
.container .offset-by-five { padding-left: 31.25%; }
.container .offset-by-six { padding-left: 37.5%; }
.container .offset-by-seven { padding-left: 43.75%; }
.container .offset-by-eight { padding-left: 50%; }
.container .offset-by-nine { padding-left: 56.25%; }
.container .offset-by-ten { padding-left: 62.5%; }
.container .offset-by-eleven { padding-left: 68.75%; }
.container .offset-by-twelve { padding-left: 75%; }
.container .offset-by-thirteen { padding-left: 81.25%; }
.container .offset-by-fourteen { padding-left: 87.5%; }
.container .offset-by-fifteen { padding-left: 93.75%; }
}