Xhorse VVDI2 2005 Discovery 3 Write Back Unused or Used Slot to CEM?

2005 Land Rover Discovery3/LR3 AKL I pulled the CEM read the data with xhorse vvdi prog and wrote back to the 5th unused slot and wrote the data back to the cem with vvdi2. Now before I go to reinstall I am second doubting myself, should I be using a used slot instead? I saw another post where they say you can use a used slot, and then another post where if you use an unused slot you just have to learn key to car when you install. Any idea?
Xhorse Vvdi2 2005 Land Rover Discovery3
Answer: You can write to unused slot and write back to CEM, works perfectly with genuine 7936, not xhorse super chip.