Iframe height forced to 400px

Hi,

My plugin is trying to output an iframe with height 100% (defined in CSS). I’m encountering the same problem described here, where AMP seems to be default the height to 400px:

https://wordpress.org/support/topic/amp-iframe-forcing-400px-height/

Unfortunately, I can’t use the height attribute because I need a % height, not pixels.

Is there a workaround for percent height, or could this be fixed in the iframe ‘sanitizer’?