The 2 helmet mode basically sets the bike up to compensate for the extra load, trying to mimic as if you were riding one up. It's really more about suspension travel than stiffness. What may help is to play around with different riding modes as those correlate directly with damping. But I guess the first question I have for you is how is the bike handling off-road and how would you rather have it behave?
I ride mine off-road about 50%, I weigh 165 with gear and I find the rear suspension to be amazing in enduro-pro mode. I also like the front suspension, but not for rocky/technical stretches. It's a bit soft, but it sure soaks up the bumps, on the flip side it's very prone to bottoming out. If I could change something it would be adding aftermarket cartridges to the front forks to increase damping.
Last question; are you standing most of the time while riding off-road?