Perhaps Scotty, Coach sommer or Ido will chime in on this...but I've not held the foundational movement on the Levers for 60 sec. I tend to rep on the moves, holding static position for about 2 sec. i don't know if you remember the Beast Skills piece talking about the planche and the need for chest strength to tighten that movement up. I think a similar situation exists here in that very strong pulling muscles/shoulder stabilizers appear to help enormously.
Keep in mind I am a hack at all of this. Scotty is much more versed and frankly smarter about progressions on all these BW strength moves.
"Survival will be neither to the strongest of the species, nor to the most intelligent, but to those most adaptable to change."