Your Vista has a 5000 lb hitch, so towing an Outback in a trailer will likely put you very close to 5000 lb hitch rating. The Outback weighs around 3500 bs (per current specs), so the trailer would have to be under 1500 lbs. Most open car trailer weigh right around 1400-1600 lbs, I think. Enclosed ones much more. A dolly would be a better fit to your hitch capacity, I think.