Very nice, BUT...
Lightly loaded, STOL droop tips, almost certainly vortex generators, stiff breeze, cool day, probably a 180HP mod.
Don't try this at home with a stock PA18, folks!
Extreme Super Cubbists are obsessive about weight and temperature and with a light cub, the right mods and the right conditions there is little you can't do.
It's an amazing aircraft, but a lot of people die in Super Cubs, which is worth remembering lest one get a trifle too carried away.
QDM