What's a ballpark overhead rate for a decent sized company? Any clues?

Would it be unethical, or...well, wrong...to vary my overhead rate depending on the job?

thanks!

by the way - if you contributed to my "Remodeling Monster" post - I have gotten two other bid requests from that builder...
One came an hour after I dropped off the "remodeling Monster" estimate. So hopefully it was becuase he liked what he saw and not because he thinks I am a sucker... [Linked Image] thanks for all the input regardless!