iFrames that resize based on the content of the page is possible for Boston.gov. In order to get them working, you will need to include a snippet of JS on the page that will be iframed. The code for this is:
<script>
window.iFrameResizer = {
targetOrigin: 'https://www.boston.gov'
}
</script>
<script src="https://www.boston.gov/sites/all/themes/custom/boston_public/dist/js/resizer.client.js"></script>