I'm running 285/75 16 KM2's and I rub under full turn and flex, but not enough for daily driving. I'm too looking to move up to 35's or 37's but I'm thinking I'll do some cut-out flares instead of lift to keep the truck as low as possible.
I've got a couple thousand miles on my Centramatics now and am impressed. I put them on at the same time as a set of BFG KM2s and anything below 60 mph is smooth as silk. I've got some vibrations above 60 or so, but may not be related to the balancers. I'm investigating those issues now.
I'd prolly call them a mild m/t.
I ran the duratracs till I changed vehicles. The only issue I had was cleaning them out. Seemed I had to spin pretty fast to get a good clean-out.
Best tire I've ever owned and I'll prolly be buying them again for the Excursion.
I think you'll need something fairly strong. What about 2" foam board? You could cut it into strips and build a perimeter box to put inside the bag.
I just picked up a bag myself. Might have to try this.