You don't need the run flat insert, but I'm gonna say you do want the Hutchinson bead lock inserts. I've heard of some folks mounting tires w/o the bead locks but it's more difficult to seat the tire and there's a risk of a tire coming off the bead while driving which could cause a loss of control.
I agree on having some kind of bead-lock insert. Knowing the tire cannot come off the rim and deflate is a piece of mind. I have the Hutchinson solid rubber beadlocks/runflats on mine and I can tell you they are tough as nails. Since I am thinking you may be running higher pressure with heavy logging etc... it is still a good piece of mind to know the tire cannot come off the rim.
When mounting the tires with these things the HEMTT wheel contacts with about 1/4" of compression of the run-flat so the tire is absolutely under compression force which keeps the bead from slipping on the wheel as well.
The 16.00R20 tire here ended up weighing 615 lbs. That is from the tire, the HEMTT two piece steel wheel and the run flat. I wanted the run-flats to ensure the tires if they ever fail will get me to where I can at least change it out without being in a hairy place or ??? just makes you have some options.
On the choice of tire sizes, I do like the 16.00R20s but they only leave just an inch of space at most between the tandems at the back. This makes it impossible to run chains. Due to this issue, I am looking into how I can extend my track bars, with some other drive train mods to make it possible to run chains on all 6 tires, as chains are an incredible benefit to getting a rig like this that is 100% reliant on traction and not momentum to get places. With being out logging your going to want to run chains no doubt.
On Valve steams I chose to use the HEMTT dual sided valve steams that allow you to fill from either side of the wheel. This is a bigger deal when you have some wheels dish side out and others dish side in. I couldn't stand the one sided steams my original tires came with and so this was a no brainier for me.
