There was another gentleman on this site (CT_Tree_Guy) who used to post. His writings were extremely helpful to me, but one day he never returned to the site (I have no idea what occurred.) I must say that I miss his insight.
Here is one more of his posts. http://www.tractorbynet.com/forums/kubota-owning-operating/68747-5030-skidder-pics-tree-bota.html
He was where I first discovered the relief valve setting for my LA853 FEL (2,560 psi) which leads me to believe that your 854 FEL would be at least that high. That is a number (2,560 psi) to start with.
Here is one more of his posts. http://www.tractorbynet.com/forums/kubota-owning-operating/68747-5030-skidder-pics-tree-bota.html
He was where I first discovered the relief valve setting for my LA853 FEL (2,560 psi) which leads me to believe that your 854 FEL would be at least that high. That is a number (2,560 psi) to start with.