I broke SassMeister with this...

html.html

<div class="container">
    <div class="left">Left A</div>
    <div class="right">Right<br><br> A</div>
    <div class="right">Right B</div>
    <div class="right">Right<br><br> C</div>
    <div class="left">Left B</div>
</div>

style.css

.container {
  overflow: hidden;
  padding: 1em;
  background: #EEE;
}

.left {
  background-color: blue;
  width: 21.62162%;
  float: left;
  margin-right: -100%;
  margin-left: 0;
  clear: none;
  clear: left;
}

.right {
  background-color: red;
  width: 75.67568%;
  float: right;
  margin-left: 0;
  margin-right: 0;
  clear: none;
}

style.scss

@import "singularitygs";

@include add-grid(2 7);

.container {
    overflow: hidden;
    padding: 1em;
    background: #EEE;
}

.left {
  background-color: blue;
  @include isolation-span(1,1);
  clear: left;
}

.right {
  background-color: red;
  @include isolation-span(1,2);
}