I noticed that my old 6.789 time actually was done on Legacy, so I decided to get an actual well deserved world record. I first beat Mumu_Didi's 6.817 with the time of 6.816 (lucky me!), then 6.798 and finally this run of 6.731.
This run is kinda crazy though! Now the first Wall Boost isn't the most perfect one, I've gotten a few times up towards 4,2k and more, although very rare. But the thing with using the right Wall Boost makes it almost impossible to even pass the corner into the last Wall Boost on such high speeds. So it's most likely not the most optimal way of doing the level, although it's more consistent for me. In the future maybe I'll need to go back to the left wall, who knows. I'm very happy with the run though, it took a bit of grinding but nothing too bad.