A tubing cutter won't cut the composite shaft, it will crush it. Have to use a hacksaw and put something inside to protect the wires.
On another note, the shafts in a Terrova, Ultrex, Ulterra cannot be changed. The center section is bonded to the shaft at MinnKota so we (ASCs) have to change the shaft and center section at the same time. The shaft/center section is shipped in as a 60" shaft and we cut them to length before building the lower unit, except for the Ulterra and due to the control boards, they're cut to length at MinnKota.