The fishhawk td arrived yesterday. I went out at lunch today and checked a couple data points at 2.5 mph in 53 feet of water on a local reservoir. On a side note, my new TR1 worked well and let me do this without messing with boat handling in 20mph winds. Line was Sunline 20lb which has a 12lb diameter. I checked the high end of the range first because that's where I thought the chart was wrong. 125 back was 38 feet with the fishhawk attached to the trutrip 40 and by sliding the probe to the diver, it measured 39 feet. On the western basin, I find that 45 back is often the 'sweet spot'. At 45 back, it was 20 feet using both methods. This is enough for me to say I now believe the published chart is correct. I'm not going to go through the motions of sampling any more data points. It's more time consuming than I expected. The fish hawk has a 'depth mode' that gives you temperatures every five feet plus the maximum depth down to the nearest foot. You have to change it to that mode for it to record max depth to the nearest foot. The next thing I'll look at is deep diving crankbaits with a snap weight. I'll only be able to tell where the weight is running. I really just want to figure out the setback to get a bandit and Reef Runner 800 running at 30 down for the times I fish the sandbar with a 2 or 3 oz snap weight.