As for sliders I do have some 1.75x.120 HREW tubing lying around that I haven't done anything with.
This will be fine for sliders, just add some more rungs(ladder design), and maybe three frame mounts than the usual two.
Up where I live (trip cities area in Washington) most of what I wheel in is mud. But I've never had an issue keeping up with the guys running 35's. I've even out wheeled some. And u was planning on taking the shorter of the two trails (Loon I believe?). I'm fine with driving down Wednesday to go in Thursday. This will pretty much be my first time on rocks though.
First time on the rocks and running the Rubicon on a weekend would be a very bad idea, it takes a completely different set of skills to wheel rocks than mud. Knowing where your vehicles corners are, where the tires are in relation to the ground, etc., is vital in keeping track of rocks once you loose sight of them. Rocks, especially with a rig set-up like yours requires you to trust a spotter without question, a trust you usually develop with guys you wheel with, not ones you just met. I would find a buddy who can make the run with you, and work together having him spot you w/hand signals, you can do it in a parking lot with soda cans, i.e. set up cans have hims spot you through without crushing them, then crushing certain ones, etc., maybe plan a run where you can wheel rocks to get some rock wheeling experience under your belt.
I am not saying you can't do it, my first time wheeling rocks was the Fordyce creek trail in my new '90 with open diffs and 31's, so I know what it is like to be in way over my head. Looking back on it I can say it was fun, but at the time it wasn't, it was a lot of hard work, and it took 8 hours to go about two miles from Meadow to Committee crossing. I will say it is nice seeing someone ask can I do it on 31's, instead of asking what tire size I need to run it. If you do decide to run it, I would find some of the old school wheelers who are going, i.e. guys who know what it takes to wheel rigs beyond their capability, and who are going in on Wednesday. Sure you wont be wheeling with the large group, but you will get to wheel at a much slower pace, without the pressure of 100 rigs behind you.