The wire strippers can't strip shielded wire and I found this idea at the EAA Homebuilders hints.
Essentially your score the insuation with a knife whilst rotating the cable or the knife, bend and twist the cable to break the insulation and remove it - 3/4" to 1" max at a time.
Pucker the shield towards you and use a pick, or in my case a narrow nail, make a hole. Pick out one cable - it helps to bend it once your pick/nail is under the wire and remove one at a time. The shield can then be returned to shape and heatshinled to insulate if required.
