I have several gi's all weighing anywhere from 3 to 5 lbs total.
I'm going with a light single weave that normally puts me right at 167lbs. But, without knowing what their scales will be at I'm going blind. I thought about brining along a small scale and seeing if they will let me weigh on theirs to calibrate mine. That way I can monitor as the day goes on. I will fight in the afternoon sometime though.
I can be at the tourmament to check things out the day before...that won't be a problem. I just hope they will let me try out their scale that day.
You don't have much time between your weigh in and your actual fight. It some cases (depending on # of competitors) it can be just a few min.