In the C-5, we took a 250 foot "line-up" penalty and a 750 foot penalty for rolling take-offs, i.e. the assumption was 250 feet to line-up off the taxyway and an additional 750 feet was added for rolling take-offs. The line-up made sense, just because of the size the the plane, but I couldn't tell after 4000 hours what difference the rolling vs. standing take-off made. A rolling take-off always had the take-off N1 established within a 800-1000 feet and acceleration from the standing start wasn't knocking anybody's heads back.
BTW, in the French-Canadian built bizjets, the FMS computes a 100 foot line-up reduction in TORA. Seems fair to me.
GF