Yes, 900psi is at max pressure. Less pressure will be less difference, but 900psi wouldn't matter if you WERE at max.
Still happily answering to the call-sign Peetza.
The problem, as you so eloquently put it, is choice.
He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.