Keep in mind that BF measurements using calipers was never really meant to give you an accurate reading (i.e. "my BF is EXACTLY 12.4%!!"). What it is good for is measuring your relative gains/losses over time. Pick a good caliper method (3site, 7site, 10 site, etc.) use it and record your results. 2 wks to a month later, repeat it.
So what if it reads 12% instead of 10%, or 12% instead of 15%? If you come back next month and it's gone down that's great!!! If it's gone up that's bad.
If you get hydrostaticly measured in a tank and wind up with an accurate BF measurement, then go home and immediately do the caliper method. Then you should have some measure to equate the two methods (ie. "O.k. so I'm 12.2% for sure, but by the calipers I'm reading 13.7%.....So 12% is rougly equal to 13 1/2% with the calipers")
Right tool for the right job