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Nice video! As I said before, my corexy build is quite similar. I also use two bronze bushings per rail on two horizontally aligned 8mm steel rods, they are press fit into my hontend carriage from each side. My way ro align them was to stick a 8mm steel rod through and heat it up on one end with a pocket torch. Then I pulled it carefully throug the bushings which melts the plastic a little bit around them. I also tried to align the two X axis rails by heating them and moving the hotend carriage close to the end mounts, so the heated rails will move closer together or farther away if needed. One thing I noticed was that after I fastened the belts, the bronze bushings will bind a bit, because the two belts i have will always have different tension. BUT : having the bushing too loose will gave artifacts in the prints because of the hotend tilting on direction changes, even if its only a fraction of a millimeter, if the carriage has a tight grip it will work better, you just have to be carefull with your jerk and acceleration. Btw. my machine can go from 0 to 90mm/s without acceleration without binding, although I can’t barely move the carriage by hand.