Hi,
Many thx for an idea.
I don't have to cable it, the only think is to setup cluster and check the mac address, and compare, which phisical port has the same mac as fpx1.
There is, unfortunately, little "but". I have to provide to dc lld, with cable plan, prior the devices will be on client's site and i cannot guess: ge-0/0/1 or maybe ge-0/0/0 (cause fxp0 has it's own dedicated port)