Okay i didnt handle a GPX6000 but i have handled GPZ , GPX5000 , GP3000 , SD2200 , 705 and i have considered making up extensions shafts to swing the battery further back on some because the ergonomics really pissed me off.
I did make up aftermarket Li-ion batteries and mounted them to the 5000 to get rid of the cable but it gave me the shitz for other reasons and i sold it last year.
You will probably get hold of one before i do so you can let us all know 😉