I have a TXI and I have to say that I don't believe your speeds either. The only way you went that fast is if you rode with a current or wind that was increasing your speed. The only true way to test speed, either with gps or radar, is to make a minimum of 2 runs in the opposite directions, and then average the 2 speeds. This way the current and wind will work with you one way and against you the next. I ride in the ocean and inland bay waters, so depending on the day, the chop and wind can vary a lot. But as close as I can determine, with gps, my TXi goes 56+ in chop, 58-59 in light chop, and 61+ on flat.