On my site, I've recently modified some code to replace the standard TextareaField for the post content when adding/editing a forum post with a WYSIWYG editor I've found. I have everything working, but the editor shows up in a small little box rather than stretching out to the sides like it does with a TextareaField. After some experimenting, I've found that when replacing the code in the TextareaField class with that of my own class, it stretches nicely, but I don't want to the editor to show up everywhere that uses a TextareaField. Is there any way to get my custom class to stretch to the sides on its own?