Best to use one, as I do (on its side). You can probably sell the spare successfully to someone else wanting to do the same.
Or just keep it as a spare - that's what I did. With 7 in use, an 8th for disaster back-up didn't seem too extravagant.
Or just keep it as a spare - that's what I did. With 7 in use, an 8th for disaster back-up didn't seem too extravagant.