what's your aim? a proportional scaling?
css solution:
<style>
.aspect-ratio-box {
height: 0;
overflow: hidden;
padding-top: calc(720/1280 * 100%);
background: white;
position: relative;
}
.aspect-ratio-box-inside {
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
}
</style>
<div class="aspect-ratio-box">
<div class="aspect-ratio-box-inside">
<!-- your **responsive** hypedivhere -->
</div>
</div>
scripted approach: Creating a Flexible Tumult Hype Document within a DIV with no set 'height' - #20 by MaxZieb