Everything before 9:09 is setup for the "run". If your hand is getting tired from trying the 11,200 block flight in one trip, you can land on one of the start rooms or the anything else not a tunnel (must be high enough above the void). Anyways mods are going have to debate over this run. Given that this uses a resource pack to get to the location to start the run. Along with the speed run time itself....

Resource pack: https://www.planetminecraft.com/texture-pack/voidflier-1-0-fly-forever-without-f3-optifine-required/