Hey,
I don't know about bathroom scales, I think they are only calibrated to be accurate between 100 and 200 lbs. What they are though is repeatable. You can weigh yourself 100 times on that same scale and it will be very close to the same. Step on a different scale and you'll get a different number. Before I'd get to upset I'd find a shipping scale and weigh it.
Rick
BTW sounds like a killer combination, got any pics?