Yup, I have two mash tuns, a 60 qt for my 5 gallon, and most average 10 gallon batches, and then I built a 120 qt mash tun for my really big 10 gallon batches - I've put upwards of 55-60# of grain in that one.
I have had issues with the braid in the 120 qt rectangular cooler though - it drains really slowly from the far end when I have a lot of grain in it, exceedingly slowly. I bought all the cpvc tubing and fittings I need to build a manifold for it, I just haven't gotten around to doing that yet. I think the issue was just how much grain the wort needed to go through to get to the drain. I even tilted it to help it, but it still took a very long time (over an hour, if I remember correctly) to drain. This is on multiple batches, and no changes to my mill gap settings. I had planned for longer brew days for these types of beers, but I would like to be able to drain more quickly than that.