Because they disappear... I find the exact same thing in open water during the summer. Absolutely slamming them from about 2hrs before sunset until just after sunset then zip, it's like a lightswitch. I've gone deeper, shallower, you name it..
We took a measurement with a fishing rod, right around 38 inches. No girth measurements taken. It also made the rounds at the local MNR office from what I've heard.
The 8spd combined with the diesel and keeping it at it's peak torque output as long as possible leads to the fantastic mileage those trucks gets. I can't wait until Ford/GMC start to offer a small displacement diesel in the half tonnes.
I was skeptical at first as well, but man it works! lol!! Like you said the blood starts to pump (they turn bright red) and after about a minute back in my gloves I'm golden.
Definitely pick up a used minivan and let someone else take that 30% depreciation hit.. Toyota, Honda, Chrysler really can't go wrong. You can get them loaded with pretty much everything.