I've removed a few while doing Duo maintenance, but only had a couple come out in one piece (maybe 30% success rate), but I haven't actually been trying to keep the insides in one piece.
The cable clamping system in Duos (back and front) is to have the cable running through a thin tube of the yellow case material which sits inside a wider outer tube of the case material, with a tubular gap in between
The black inserts (battery box and headset) include a tapered tube sticking out of the back which the cable runs through, and which forms a 'circular wedge'.
A cross-section through this system is:
When the insert is pushed into the housing, the black wedge compresses the inner yellow tube at the end, clamping and sealing the cable.
In the rear battery box, even if all the yellow 'melt retainers' were drilled carefully with a long thin bit, out, the wedge may still be tricky to pull out as a straight pull - careful pulling around the cable insert area.
My repairs have involved throwing all the internals away to be replaced with a 3-cell holder and fitting a new cable, so I haven't been concerned about the cable or keeping the insides in one piece
I start off by drilling out the yellow insert retainer blobs, then cutting the cable inside the box with the tip of a knife blade, which stops the wires from pulling down the insert edges as the insert is removed.
If the insert came out OK and the old cable was removed from the base, the inner yellow tube could possibly be opened out at the end by careful use of a screwdriver or other round rod to allow a new cable to be re-inserted.
I really wouldn't know how easily the insert would go back in with a new cable, since I've always done a complete replacement with a 3-cell holder.
For most modern LED inserts (ie Bisun Flexitwin and (as far as I know) most CustomDuo inserts) a 3-cell holder provides sufficient voltage, and that isn't too hard to do (just needs some plastic milling out of the box base to give enough height for the holder).
That does mean that as long as you don't actually break the case, there could be a decent plan B even if your insert comes out in pieces.
If you want more details, reply soon as I'm off to Slovenia in a few days.
