I'd also say that really for that sort of work, a vintage machine is not really appropriate. A 15 or 27 with the big hand wheel -might- do it for a bit but they're not made for that and it's very hard on the machines long term. What Miriam was saying more gently than I will is that you're doing industrial work - use an industrial. If the leashes are mostly webbing, you might get away with the vintage machine for a while - but when it fails it will be when you most need it. If there's leather, etc just get a machine appropriate for the job.
It's like using a Toyota Camry to haul all of the shingles you need for your roof. It'll do it once or twice but you'll prefer the job that the full sized truck does and the truck will last longer doing the work you want it to.