Carrying pallets 2 high is high risk. Rated distance is also measured vertically so if centre of mass is greater than the rated distance the forklift capacity has to be down rated. Then there are the issues of the driver's view being obstructed, risk of items falling backwards onto operator if load above load guard; risk of items being unstable on forks and falling forward under braking or sideways in turns; fact that the 2nd pallet load is likely to hit a persons upper torso/ head with much increased risk of death or disabling injury...