i find it interesting that he contributes his success in 3x3 speedsolve to 4x4. i was stuck at around 20 for a long time as well, but after a long time of practicing big cubes 4,5 for almost 5 months with barely touching a 3x3, i dropped sub 20 after that easily for some reason. it just seems so easy to turn the cube and the lookahead skill is developed a lot when doing bigcubes. very interesting.