Mrs JJ here - Gary is in KC for work/training.
We do occasionally get high-centered - the worse I remember was just this year on the flat in front of Otter Creek - it took forever to get off of the stump - Gary kept circling but I don't think we had to start the big motor. That was the same trip that we saw a boat coming from up the river and they cut across that flat and got stuck on the island there. It is a wonder they didn't hit some stumps as many as there are on that flat.
It seems to be more of a problem as the water gets lower since more of the shorter stumps begin appearing.