Originally Posted by Bobby_M
Caving is an issue when you pump out of the mash tun. The weight of the grain itself is not a problem.
+1 on that as a Herms brewer.
I brewed a beer last weekend that out of a 33# grain bill had 17# of flaked wheat and oats, and since my tun is only 15.5g the mash was way too thick even with 2# of rice hulls. I had to stir it about every 10 minutes to keep it from sticking.
At no point was I worried about my J-bird false bottom or stand collapsing. It's a tank.
As for height. You need to either have tall enough to place the false bottom, just above or below your dip tube. Above means you can stir it without worry that you'll knock out your dip tube, but you will loose usable mash volume. Below minimizes dead space, but you need to be mindful of your dip tube when stirring the mash.
The choice is entirely yours.