I had never until today seen instructions for a splice technique for parallel core ropes. Mind blowing. Seems like extracting the core strands is the challenge, as that sheath is tight as all get-up.
There are a couple splices, New England Rope’s Heavy Duty Kernmantel, and Marlow’s Vega splice.
Making a covered, naked eye splice eliminates needing to bring the core strands through the cover, I spliced Tech Cord this way.