Embed Comments - Resize comments Iframe


I use Ghost + Discourse together, I unlocked the commenting feature on posts.
When we use external integration of dicourse we can choose a class.
When I try to change padding on this class (in embed css in discourse), the comments iframe does not scale well… (height is not good… it miss padding)

Is there a way to scale better this Iframe ? Or have I to deal with JS ?
For example i can’t have a larger button in order to “continue the discussion”.

Thanks !