I don't have a DK50SE Cab (unfortunately, as it's a great tractor...ran one briefly a while back), but I did a pretty controlled experiment along these lines somewhat unintentionally. The steel block that I sourced from the local scrap yard to make into my counterweight weighed exactly 1,300lbs. We transported it home in my neighbor's dump truck, and I drove my tractor with FEL and forks over to his place to weld the block into a counterweight. We had dumped the block of steel onto some sections of 4x4, and I was able to just barely lift it with the FEL without lifting the rear tires (level concrete). I didn't have anything on the 3pt because I was going to be driving back with the counterweight on my tractor. Also, my rear tires aren't loaded. My loader is rated at lifting 2,638lbs to max height (at the pins). The rear tires were pretty darned light, and an abrupt move on the FEL control, or the HST control would cause the tires to raise.
So, with all that, I'd say probably something in the ballpark of half the listed max lift would be doable on a flat, level surface if you're careful.