<div class="row-fluid">
@foreach (var c in fs.Containers)
{
<div class="umbraco-forms-container @("col-md-" + c.Width)">
...
in theme default - form.cshtml
for the cols. it’s pretty rudimentary.. 1 col for anything below the md breakpoint.
But knowing this your css could override the col-md-4, with breakpoint options?