They are currently a bit too short, and content gets small due to a high aspect ratio:
Here is an example (but in this one the content does not get small because I’ve mitigated it, content stays the same size regardless of view dimensions):
That’s a nice workaround, but every user would have to do that manually for every single post, and then we’ll have codepen embeds of all sorts of varying sizes across the forums if they do it.
That would still be useful in some cases, but having a better default size would help a lot more out of the box. Plus its easy, just a simple CSS addition to the site.