Resize images in existing posts

So when you regenerated the thumbnails, did you use a plugin like:
WordPress Regenerate Thumbnails plugin.
Or did you make them in some other fashion? I’ve used this plugin before and it seemed to work for me.

Another possible way to do this is with making a style modification in your style.css file. You can overwrite the img.size-large style and force it to a particular width:

img.size-large { width: 600px !important; }

Doing this though might have unexpected results. Perhaps an image has inline styling and such. But it’s worth a try.

Let us know if this worked or not.

Chris