That’s because people can ruin tanks going lower if they aren’t patient and careful. Pressure is more and more potentially damaging the lower get you go. It also makes evenly sanding with higher grit more important. Just depends on comfort, skill and how much it bugs ya. I have a current build thread of the same size tank and took it down to 600 if memory serves correct.How low of a grit would you go? Most vids and posts only go as far as 1000.
99% of people should probably stick to 1k/2k.