For an IFrame inclusion, I used the library https://github.com/davidjbradshaw/iframe-resizer
However be aware that Mendix uses cookies, and since Safari (both desktop/mobile) and Internet Explorer block cookies in Iframes when that Iframe is loaded from a different domain by default, you will not be able to use your Mendix application in those browsers. I did file a support ticket about this with Mendix but they were unable to resolve this for the cloud environment.