I recently upgraded to Vegas 5. I tried to render a video file as a NTSC DVDA Video stream template. Everytime I set custom bit rates and click ok, it returns to the default template. I've checked the options/preferences tab but don't see any place to set templates as defaults.
You can't change the default templates. However, you can add a new template with your custom settings and then choose that template each time. Type a new name for your template and click the floppy disk icon to save it.