I learned flairs in a pipe that had giant dirt and gravel patches in the flat bottom. Pretty sure 80% of pipes in North America are terribly maintained.
id have to say 3 fet with a tail. but personally i think pipe skiing is dying because most skiers and snowboarders rarely ski it even if they do have one accessible. and when people dont use it resorts loose it. just my 2 cents.
One time i was in the pipe on the first hit i tryed to air out not doing a trick but didnt see the giant hole on top of the pipe. When i went up both skis got lodged and i poped out doing a backflip. and landed it, im pretty sweet.