I may be wrong, but 1X19 is not for halyards. It is relatively ridgid and used mostly for stays. If you are trying to bend this around a shiv, you are likely going to see premature breaking due to bending it so tightly. 7X19 is normally used for halyards because it is much more flexible.
Either way the breaking strength of 1X19 wire or 7X19 is 2100 or 1780 lbs respectively for 1/8 inch wire. While 4mm (slightly smaller than 1/8) V-12 has a breaking strength of 3500 lbs. So theoretically to get the same holding power you could go down to 3mm with a breaking stength of 1900lbs. Of course line this small would be very difficult to work with, but then just put a larger core over part of the V12 and you get a stronger halyard, eliminate weight, eliminate the possibility of meat hooks gashing someone, and the whole thing will likely cost less than wire.
In other words, I would recommend against wire, and go to high tensil line.
