Back in the late 60's, during the transition period, Jeff Hakman said something like, "Trim is now defined as being in the steepest part of the wave." Meaning...as opposed to standing on the forward portion of your board.
It was a keen observation.
This shot is kind of along those lines. Even though he isn't forward on his board, you can definitely say he's "in trim."
Continuing the discussion regarding "the knuckle" which was/is one the tenants of Greenough board design...
I came across this mid-70's shot of Jeff Hakman dropping in at Pipeline. The "stock" rocker set up from that era -- apex well forward, with a semi-straight bottom curve running through the tail -- accomplished two things at once. It was flat enough, nose to tail, to generate a lot of lift and drive, while at the same time had enough of a "bump" in the front 1/4 to handle serious adversity...as is clearly visible here.
Today's boards have done away with the forward apex/knuckle, and settled for an overly generous curve running nose to tail that doesn't come close to maximizing the rocker's potential.