I think your cable retrieve/ratio would be minute at best. Personally, I would not splice. That will set you up for more frays and kinks in your cable and may cause a jam lowering. You'll be better off spending the money for a larger spool of wire

Downriggin'
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"If you are not scratchin bottom, you ain't fishing deep enough!" -DR

Puget Sound Anglers, Gig Harbor Chapter