how to get certain position from encorder for Rslogix desinger

Hi, everyone:
we need help for this issue, we need this position to redefine motion position with MRP instruction, we use kinetix350 CIP motion. we want to use the same registration input (photo sensor), but the registration position and above position are not at the same spot.
Thanks!

this is existing conveyor system, since at certain spot the length of the conveyor is short , so need to redefine its position.

this is overhead conveyor system,it has 250 carrying racks, we have encoder on the conveyor to feedback its position, it has one loader and one unloader which controlled by PLC,since the line stretched, we cut portion of the chain, now one rack can't use any more, also that section is short, it gives us problem when the line goes through the loader and unloader at that spot( the loader and unloader are next each other), we need to redefine certain position to fix this problem.at first we need to get a certain position from encoder then redefine this position.
thanks!

can we use GSV and SSV to get this position?
thanks!