Yup, it really helps to drop the tires down to 20psi. I was out on the beach quite a bit last week and the truck worked too hard and came real close to getting stuck at the factory pressure (35/42). I actually tried to leave it at factory because my dealer suggested that the Sand mode should handle everything I needed and I risk the low profile tires coming off the rims (?) if I drop the pressure too much. In any event, there was a gas station as soon as I got off the beach each day so I'd pump them back up relatively soon.
BUT, I did get "stuck." First time on the soft beach the truck drove okay but I parked it in sand which I found to be too soft. After a few hours on the beach when I started it up again I couldn't get out of my "spot." I then dropped the pressure down further than I had it (down to 20PSI), had a push from a couple friends and was able to get it out without a tow. I was not buried to the frame but found that I could only go back and forth a couple feet. Even when I tried to dig a nice path, pack things down, switch in 4 Low, try DSC on and off, etc....I just needed lower pressure and a push.
The rest of the week I always dropped the pressure and kept to parking on firm beach or in established tracks.
IMO the truck needs bigger tires and/or a more aggressive tread. That tire is just too slick for this heavy of a vehicle. I have an HSE so I'm open to suggestions when they need replaced.