Who out there shoots portraits with their 8x10? What focal length lens do you r egularly use or like to use?

I currently have the option of purchasing a 480mm lens for my 8x10 camera, but a m wondering whether the focal length is too long. I would like to use the lens to shoot people half-figure, and have determined that at this size I am about 6 feet from my subject, with a bellows extension of about 25 inches. I have pretty long arms, but with this amount of bellows extended I was barely able to both l ook through the back of the camera AND adjust the front standard of the camera a t the same time, to good effect. The camera's stability, with its front and rear standards extended within 5 inches of their maximum distance, was also somewhat compromised (the camera took about 5 seconds to settle after the dark slide was pulled). To be sure, I WOULD like to get a longer lens for shooting portraits than the standard 305mm I already have, but am wondering whether 480mm is simply TOO long for such purposes. How do 8x10 format portraitists use such long focal lengths--or even longer, for that matter--for shooting portraits comfortably an d easily? Maybe they have an assistant, but I don't have a second person to wor k the front or back of the camera--and, to boot, would like to be able to focus and shoot pretty fast to catch people's expressions. Doubling the standard focal length in a 4x5 format from 150mm to 300mm, and using a 300mm lens to shoot por traits in 4x5 seems relatively easy, but applying the same principle to 8x10 see ms alot more daunting if not perilous. Any suggestions? Opt for a shorter long lens or adapt to 480mm?