My old Durango had two spares; One mounted on the rear bumper, and the other mounted under the trailer with a cable lift/lock system. Of course, a little experience with the 15" china bombs made having 2 spares a good idea.
When I traded the Durango in on the Silverback, I kept the bumper mount, and moved the Silverback spare to the rear bumper. The vinyl cover I had for the 15" tire was able to stretch over the new 16" tire easily. It worked out well, and it moved about 60 pounds (feels like 120 pounds) aft. Now the trailer is carrying the weight of it's spare instead of truck.
2016 Ford F-350 Lariat CC, 4x4 SRW. B&W turnover with extender. 2015 CC Silverback 29RE, fitted with Reese Goose Box. Amateur Extra Class K5TS, 2016 nights camped 16