in our unit in the Navy there was a guy who disputed his bf% as measured by the tape. He was a pretty big guy approx. 290lbs or so and the tape method had him over 30% bf%.
He entered his dispute in and they sent him out for the hydrostatic test and got him dipped and his percentage ended up being around 18%. This was many years ago so i don't remember the exact process, but i do know it's possible to dispute the tape measure method.
Hope that helps.
Corn