I'm not. That's why I do tend to follow the OEM recommendations when it comes to payload and towing.
You think like an engineer, which is good. I'm an ME, and naturally have massive respect for the engineering hours OEMs put into a production vehicle.
However, we should also realize the limitations engineers have in the corporate hierarchy. Not every payload and towing spec is driven by engineering; legal and marketing have the final say, for good and bad reasons.
Well, I think you've provided solutions to your own problem there. If your over GVWR, you probably need to do one of two things: 1) cut back on the weight or 2) get a new platform.
IMO a LX470 should be more than enough to tour and overland with for 2 people + gear. Honestly, it sounds to me like you're cramming more gear on it than it was meant to carry. It's not a UTE or pickup. It's a luxury SUV. If I were using that vehicle to travel with, I'd ditch the RTT, go with 32"s vs 33"s, lose the rear bumper, and analyze which of gear can be cut (e.g. 100lbs for a fridge + food sounds like a lot). Or if you're absolutely deadset on keeping all of that armor and gear, get a good offroad trailer to free up some payload. Your mpg can't possibly be doing well with that kind of setup either.
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Someone in that kind of situation definitely has options to deal with the payload issue. I'm not an auto engineer (and I'm willing to bet most others on here aren't either) so I'm not going to try and guess where I can cheat with extra weight. When it comes to mpg, handling, braking, stability, and overall safety, it's just not an issue I want to take a chance on. If you're okay doing that, that's your choice I guess.
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Keep in mind the above was NOT my rig. It's a fictional build to explain why I feel 75% of rigs on here are over GVW.
My LC was bone stock except for 32s, and has taken me to where ever I needed to go (I don't rock crawl). My current platform? A lowly 2006 Exporer with the 3rd row removed. Payload is ~1500 lbs, and I've never gotten anywhere near.
As to cheat points, here is my somewhat educated opinion: go by axle capacities (GAWRs). This is one area where marketing and legal departments care least about - how many Superbowl commercials brag about the rear GAWR on a pickup?
In the DOT commercial world, payload is ONLY determined by GAWRs. A trucks GVW is always equal to sum of its GAWRs. A Kenworth does not have "payload" anywhere in its brochure. The GAWR rating from an OEM encompasses all of the following: suspension capacity, braking capacity, tire capacity, and bearing / drivetrain capacity. Therefore, as long as you don't exceed your front and rear GAWRs, you haven't exceeded the safety design criteria of your truck.
I'll provide an example: why does a 6.4 Hemi RAM 2500 have more payload that a 5.7 Hemi? Axles, frame, transmission, transfer case, every component is identical, except the softer springs purposely chosen for the 5.7 truck. Obviously this is a marketing driven specification. They want you to upgrade to the larger engine.
