This might be a little late — hope you’ve already explored.
I’ve been on sand lake dunes a couple times. You can get an off road permit at a few of the local gas stations on the drive to the dunes - they last a year. Just google OR ohv permit.
You can get a flag at a motorcycle supply store. You have to be creative with the mounting. I clamped it on my roof rack rail.
There’s a good staging area to air down. (If you don’t air down, you’ll be like everybody else stuck as soon as they get off the cement). I ran 15-18 psi, rear locker, traction control off, use manual shifting to keep the revs between 4-6k where the engine builds a bit of HP when you are trying a dune climb.
Watch your roll over angles as things get deceptive in the sand.
Bring a shovel, buddy and traction device if you aren’t used to running in the sand.
It’s a hoot out there; you’ll quickly discover why you need more dampening and everything in the cab needs to be strapped down firmly.
Have fun —
