I'd do as suggested and order a bit overlong with swages for the top end and use mechanical for the bottom end. The mechanical fittings (Sta-Lok, Hayn, etc) are easy to use. I wouldn't oversize unless changing every fitting, on mast as well as possibly the chainplates. Rigging should be set up to about 20% of its max working load and larger wire will have more loads. More load and a drilled out fitting with less meat around the hole is a bad combination.
Living aboard in Victoria Harbour